$ bundle exec standardrb

standard: Use Ruby Standard Style (https://github.com/standardrb/standard)
  app/admin/rooms.rb:33:9: Style/RedundantInterpolation: Prefer `to_s` over string interpolation.
  app/controllers/application_controller.rb:12:30: Style/SafeNavigation: Use safe navigation (`&.`) instead of checking if an object exists before calling the method.
  app/controllers/participants_controller.rb:84:7: Style/IdenticalConditionalBranches: Move `redirect_to root_path` out of the conditional.
  app/controllers/participants_controller.rb:87:7: Style/IdenticalConditionalBranches: Move `redirect_to root_path` out of the conditional.
  app/helpers/schedules_helper.rb:27:19: Style/SlicingWithRange: Prefer `[split..]` over `[split..-1]`.
  app/mailers/notifier.rb:1:7: Rails/MailerName: Mailer should end with `Mailer` suffix.
  app/mailers/notifier.rb:1:18: Rails/ApplicationMailer: Mailers should subclass `ApplicationMailer`.
  app/mailers/notifier.rb:7:21: Rails/TimeZone: Do not use `Time.now` without zone. Use one of `Time.zone.now`, `Time.current`, `Time.now.in_time_zone`, `Time.now.utc`, `Time.now.getlocal`, `Time.now.xmlschema`, `Time.now.iso8601`, `Time.now.jisx0301`, `Time.now.rfc3339`, `Time.now.httpdate`, `Time.now.to_i`, `Time.now.to_f` instead.
  app/models/admin_user.rb:1:19: Rails/ApplicationRecord: Models should subclass `ApplicationRecord`.
  app/models/attendance.rb:1:20: Rails/ApplicationRecord: Models should subclass `ApplicationRecord`.
  app/models/attendance.rb:7:26: Rails/RedundantPresenceValidationOnBelongsTo: Remove explicit presence validation for `session_id`.
  app/models/attendance.rb:8:30: Rails/RedundantPresenceValidationOnBelongsTo: Remove explicit presence validation for `participant_id`.
  app/models/categorization.rb:1:24: Rails/ApplicationRecord: Models should subclass `ApplicationRecord`.
  app/models/category.rb:1:18: Rails/ApplicationRecord: Models should subclass `ApplicationRecord`.
  app/models/code_of_conduct_agreement.rb:1:32: Rails/ApplicationRecord: Models should subclass `ApplicationRecord`.
  app/models/event.rb:1:15: Rails/ApplicationRecord: Models should subclass `ApplicationRecord`.
  app/models/event.rb:38:34: Style/RedundantSort: Use `min_by` instead of `sort_by...first`.
  app/models/event.rb:59:26: Lint/AssignmentInCondition: Wrap assignment in parentheses if intentional
  app/models/level.rb:1:15: Rails/ApplicationRecord: Models should subclass `ApplicationRecord`.
  app/models/markdown_content.rb:1:25: Rails/ApplicationRecord: Models should subclass `ApplicationRecord`.
  app/models/participant.rb:1:21: Rails/ApplicationRecord: Models should subclass `ApplicationRecord`.
  app/models/presentation.rb:4:22: Rails/ApplicationRecord: Models should subclass `ApplicationRecord`.
  app/models/presentation.rb:8:23: Rails/RedundantPresenceValidationOnBelongsTo: Remove explicit presence validation for `session`.
  app/models/presentation.rb:9:30: Rails/RedundantPresenceValidationOnBelongsTo: Remove explicit presence validation for `participant_id`.
  app/models/presenter_timeslot_restriction.rb:1:38: Rails/ApplicationRecord: Models should subclass `ApplicationRecord`.
  app/models/presenter_timeslot_restriction.rb:5:27: Rails/RedundantPresenceValidationOnBelongsTo: Remove explicit presence validation for `timeslot_id`.
  app/models/presenter_timeslot_restriction.rb:6:30: Rails/RedundantPresenceValidationOnBelongsTo: Remove explicit presence validation for `participant_id`.
  app/models/room.rb:1:14: Rails/ApplicationRecord: Models should subclass `ApplicationRecord`.
  app/models/room.rb:9:24: Rails/RedundantPresenceValidationOnBelongsTo: Remove explicit presence validation for `event_id`.
  app/models/room.rb:11:3: Rails/UniqueValidationWithoutIndex: Uniqueness validation should have a unique index on the database column.
  app/models/session.rb:1:17: Rails/ApplicationRecord: Models should subclass `ApplicationRecord`.
  app/models/session.rb:34:24: Rails/RedundantPresenceValidationOnBelongsTo: Remove explicit presence validation for `event_id`.
  app/models/session.rb:35:30: Rails/RedundantPresenceValidationOnBelongsTo: Remove explicit presence validation for `participant_id`.
  app/models/session.rb:121:26: Rails/WhereEquals: Use `where(id: recommended.map { |r| r[1] })` instead of manually constructing SQL.
  app/models/session.rb:121:58: Rails/Pluck: Prefer `pluck(1)` over `map { |r| r[1] }`.
  app/models/session.rb:150:8: Rails/WhereEquals: Use `where(session_id: sessions_by_id.keys)` instead of manually constructing SQL.
  app/models/settings.rb:1:18: Rails/ApplicationRecord: Models should subclass `ApplicationRecord`.
  app/models/settings.rb:117:14: Rails/TimeZone: Do not use `Time.parse` without zone. Use one of `Time.zone.parse`, `Time.current`, `Time.parse.in_time_zone`, `Time.parse.utc`, `Time.parse.getlocal`, `Time.parse.xmlschema`, `Time.parse.iso8601`, `Time.parse.jisx0301`, `Time.parse.rfc3339`, `Time.parse.httpdate`, `Time.parse.to_i`, `Time.parse.to_f` instead.
  app/models/settings.rb:118:14: Rails/TimeZone: Do not use `Time.parse` without zone. Use one of `Time.zone.parse`, `Time.current`, `Time.parse.in_time_zone`, `Time.parse.utc`, `Time.parse.getlocal`, `Time.parse.xmlschema`, `Time.parse.iso8601`, `Time.parse.jisx0301`, `Time.parse.rfc3339`, `Time.parse.httpdate`, `Time.parse.to_i`, `Time.parse.to_f` instead.
  app/models/settings.rb:125:27: Rails/TimeZone: Do not use `Time.parse` without zone. Use one of `Time.zone.parse`, `Time.current`, `Time.parse.in_time_zone`, `Time.parse.utc`, `Time.parse.getlocal`, `Time.parse.xmlschema`, `Time.parse.iso8601`, `Time.parse.jisx0301`, `Time.parse.rfc3339`, `Time.parse.httpdate`, `Time.parse.to_i`, `Time.parse.to_f` instead.
  app/models/settings.rb:126:25: Rails/TimeZone: Do not use `Time.parse` without zone. Use one of `Time.zone.parse`, `Time.current`, `Time.parse.in_time_zone`, `Time.parse.utc`, `Time.parse.getlocal`, `Time.parse.xmlschema`, `Time.parse.iso8601`, `Time.parse.jisx0301`, `Time.parse.rfc3339`, `Time.parse.httpdate`, `Time.parse.to_i`, `Time.parse.to_f` instead.
  app/models/timeslot.rb:1:18: Rails/ApplicationRecord: Models should subclass `ApplicationRecord`.
  app/models/timeslot.rb:8:24: Rails/RedundantPresenceValidationOnBelongsTo: Remove explicit presence validation for `event_id`.
  lib/scheduling/context.rb:69:7: Rails/Output: Do not write to stdout. Use Rails's logger if you want to log.
  lib/scheduling/context.rb:69:74: Style/LineEndConcatenation: Use `\` instead of `+` to concatenate multiline strings.
  lib/scheduling/schedule.rb:129:7: Rails/Output: Do not write to stdout. Use Rails's logger if you want to log.
  lib/scheduling/schedule.rb:179:11: Rails/Output: Do not write to stdout. Use Rails's logger if you want to log.
  lib/scheduling/schedule.rb:182:13: Rails/Output: Do not write to stdout. Use Rails's logger if you want to log.
  lib/scheduling/schedule.rb:182:55: Style/LineEndConcatenation: Use `\` instead of `+` to concatenate multiline strings.
  lib/scheduling/schedule.rb:200:9: Rails/Output: Do not write to stdout. Use Rails's logger if you want to log.
  lib/scheduling/schedule.rb:201:9: Rails/Output: Do not write to stdout. Use Rails's logger if you want to log.
  lib/scheduling/schedule.rb:203:11: Rails/Output: Do not write to stdout. Use Rails's logger if you want to log.
  lib/scheduling/schedule.rb:205:9: Rails/Output: Do not write to stdout. Use Rails's logger if you want to log.
  lib/scheduling/session_set.rb:19:7: Style/SafeNavigation: Use safe navigation (`&.`) instead of checking if an object exists before calling the method.
  lib/tasks/app.rake:114:17: Rails/FindEach: Use `find_each` instead of `each`.
  lib/tasks/app.rake:229:42: Performance/Detect: Use `find` instead of `select.first`.
  lib/tasks/app.rake:231:102: Style/LineEndConcatenation: Use `\` instead of `+` to concatenate multiline strings.
  lib/tasks/app.rake:239:14: Lint/MixedRegexpCaptureTypes: Do not mix named captures and numbered captures in a Regexp literal.
  lib/tasks/app.rake:294:12: Style/RedundantInterpolation: Prefer `to_s` over string interpolation.
  lib/tasks/app.rake:295:48: Rails/WhereEquals: Use `where(event_id: event.id)` instead of manually constructing SQL.
  lib/tasks/app.rake:301:67: Style/LineEndConcatenation: Use `\` instead of `+` to concatenate multiline strings.
  lib/tasks/app.rake:302:39: Style/LineEndConcatenation: Use `\` instead of `+` to concatenate multiline strings.
  lib/tasks/app.rake:310:5: Style/GlobalStdStream: Use `$stdout` instead of `STDOUT`.
  lib/tasks/app.rake:312:13: Style/GlobalStdStream: Use `$stdin` instead of `STDIN`.
  lib/tasks/app.rake:315:7: Style/GlobalStdStream: Use `$stdout` instead of `STDOUT`.
  lib/tasks/app.rake:317:7: Style/GlobalStdStream: Use `$stdout` instead of `STDOUT`.
  lib/tasks/app.rake:358:15: Style/GlobalStdStream: Use `$stdout` instead of `STDOUT`.
  lib/tasks/app.rake:391:108: Style/LineEndConcatenation: Use `\` instead of `+` to concatenate multiline strings.
  lib/tasks/app.rake:394:53: Style/LineEndConcatenation: Use `\` instead of `+` to concatenate multiline strings.
  lib/tasks/app.rake:395:158: Style/LineEndConcatenation: Use `\` instead of `+` to concatenate multiline strings.
  lib/tasks/app.rake:414:19: Style/HashConversion: Prefer `ary.to_h` to `Hash[ary]`.
  lib/tasks/app.rake:426:25: Style/GlobalStdStream: Use `$stdin` instead of `STDIN`.
  lib/tasks/app.rake:462:37: Performance/Count: Use `count` instead of `select...count`.
  lib/tasks/app.rake:481:38: Performance/Detect: Use `find` instead of `select.first`.
  lib/tasks/app.rake:492:39: Rails/TimeZone: Do not use `Time.now` without zone. Use one of `Time.zone.now`, `Time.current`, `Time.now.in_time_zone`, `Time.now.utc`, `Time.now.getlocal`, `Time.now.xmlschema`, `Time.now.iso8601`, `Time.now.jisx0301`, `Time.now.rfc3339`, `Time.now.httpdate`, `Time.now.to_i`, `Time.now.to_f` instead.
  lib/tasks/app.rake:619:28: Lint/AssignmentInCondition: Wrap assignment in parentheses if intentional
  spec/controllers/participants_controller_spec.rb:70:91: Rails/TimeZone: Do not use `Time.now` without zone. Use one of `Time.zone.now`, `Time.current`, `Time.now.in_time_zone`, `Time.now.utc`, `Time.now.getlocal`, `Time.now.xmlschema`, `Time.now.iso8601`, `Time.now.jisx0301`, `Time.now.rfc3339`, `Time.now.httpdate`, `Time.now.to_i`, `Time.now.to_f` instead.
  spec/features/interest_gathering_spec.rb:5:127: Rails/TimeZone: Do not use `Time.now` without zone. Use one of `Time.zone.now`, `Time.current`, `Time.now.in_time_zone`, `Time.now.utc`, `Time.now.getlocal`, `Time.now.xmlschema`, `Time.now.iso8601`, `Time.now.jisx0301`, `Time.now.rfc3339`, `Time.now.httpdate`, `Time.now.to_i`, `Time.now.to_f` instead.
  spec/features/manage_your_profile_spec.rb:5:55: Rails/TimeZone: Do not use `Time.now` without zone. Use one of `Time.zone.now`, `Time.current`, `Time.now.in_time_zone`, `Time.now.utc`, `Time.now.getlocal`, `Time.now.xmlschema`, `Time.now.iso8601`, `Time.now.jisx0301`, `Time.now.rfc3339`, `Time.now.httpdate`, `Time.now.to_i`, `Time.now.to_f` instead.
  spec/features/sign_in_and_out_spec.rb:4:78: Rails/TimeZone: Do not use `Time.now` without zone. Use one of `Time.zone.now`, `Time.current`, `Time.now.in_time_zone`, `Time.now.utc`, `Time.now.getlocal`, `Time.now.xmlschema`, `Time.now.iso8601`, `Time.now.jisx0301`, `Time.now.rfc3339`, `Time.now.httpdate`, `Time.now.to_i`, `Time.now.to_f` instead.
  spec/models/event_spec.rb:4:50: Rails/Date: Do not use `Date.today` without zone. Use `Time.zone.today` instead.
  spec/models/settings_spec.rb:31:96: Style/LineEndConcatenation: Use `\` instead of `+` to concatenate multiline strings.
  spec/spec_helper.rb:19:1: Rails/RootPathnameMethods: `Rails.root` is a `Pathname`, so you can use `Rails.root.glob("spec/support/**/*.rb")`.
standard: Run `standardrb --fix` to fix up to 79 problems.