Validate unit badge ID with badge_id_valid and improved error messages

[stefan-burke]

Summary

• Replaces a custom badge-id validation callback with a standard Rails validation method badge_id_valid to provide clearer error messages.
• Adds a dedicated badge existence check via badge_id_valid that surfaces a localized error when a non-existent badge ID is used.
• Adds validation for blank IDs so an empty badge ID also surfaces a validation error.
• Updates UI error display to show a list of relevant validation errors.

Changes

Model

• Remove before_create :validate_badge_id callback.
• Add validation :badge_id_valid, on: :create, if: -> { unit_badges_enabled? }.
• Implement new method badge_id_valid to verify Badge.exists?(id: id) and add a localized error on :id if not found; also returns an error when id is blank.
• Minor normalization tweak in normalize_id to guard against blank IDs (no behavioral change).

Views

• Update app/views/shared/_save_message.html.erb to render a list of errors when provided, improving visibility of validation issues.

Tests

• Update spec/models/unit_spec.rb to reference the new #badge_id_valid validation (renamed from #validate_badge_id).
• Minor test adjustments in spec/services/s3_backup_service_spec.rb to accommodate test helper changes and ensure directories exist when creating test artifacts.

Test plan

• With unit badges enabled, attempting to create a Unit with a non-existent badge ID should fail with the message defined by units.validations.invalid_badge_id on the id field.
• Ensure that when id is blank, the badge existence check is not triggered.
• Verify that the UI save message area renders a list of validation errors when present.

Notes

• The i18n key units.validations.invalid_badge_id should be defined to provide the user-friendly error message.
• No user-facing API changes beyond improved validation messaging and error display.
• Additional minor test adjustments were included to align with the new validation approach.

🌿 Generated by Terry

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📎 Task: https://www.terragonlabs.com/task/6c5d54cd-3d8f-4cb1-a6c4-1599a73e07cc