Improve default action mailer configuration (rails#52513)

* Suggest using Rails credentials for STMP username and password

* Set a default host for mailer template links in production too

* Homogenize comment of mailer link host setting

* Just use the default from address set by ApplicationMailer

Author: dhh

railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt

@@ -45,6 +45,7 @@ Rails.application.configure do
   # caching is enabled.
   config.action_mailer.perform_caching = false
 
+  # Set localhost to be used by links generated in mailer templates.
   config.action_mailer.default_url_options = { host: "localhost", port: 3000 }
   <%- end -%>
 

railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt

@@ -91,6 +91,18 @@ Rails.application.configure do
   # Set this to true and configure the email server for immediate delivery to raise delivery errors.
   # config.action_mailer.raise_delivery_errors = false
 
+  # Set host to be used by links generated in mailer templates.
+  config.action_mailer.default_url_options = { host: "example.com" }
+
+  # Specify outgoing SMTP server. Remember to add smtp/* credentials via rails credentials:edit.
+  # config.action_mailer.smtp_settings = {
+  #   user_name: Rails.application.credentials.dig(:smtp, :user_name),
+  #   password: Rails.application.credentials.dig(:smtp, :password),
+  #   address: "smtp.example.com",
+  #   port: 587,
+  #   authentication: :plain
+  # }
+
   <%- end -%>
   # Enable locale fallbacks for I18n (makes lookups for any locale fall back to
   # the I18n.default_locale when a translation cannot be found).

railties/lib/rails/generators/rails/app/templates/config/environments/test.rb.tt

@@ -44,9 +44,8 @@ Rails.application.configure do
   # ActionMailer::Base.deliveries array.
   config.action_mailer.delivery_method = :test
 
-  # Unlike controllers, the mailer instance doesn't have any context about the
-  # incoming request so you'll need to provide the :host parameter yourself.
-  config.action_mailer.default_url_options = { host: "www.example.com" }
+  # Set host to be used by links generated in mailer templates.
+  config.action_mailer.default_url_options = { host: "example.com" }
 
   <%- end -%>
   # Print deprecation notices to the stderr.

railties/lib/rails/generators/rails/authentication/templates/mailers/passwords_mailer.rb

@@ -1,6 +1,6 @@
 class PasswordsMailer < ApplicationMailer
   def reset(user)
     @user = user
-    mail subject: "Reset your password", to: user.email_address, from: "[email protected]"
+    mail subject: "Reset your password", to: user.email_address
   end
 end

railties/lib/rails/generators/rails/credentials/templates/credentials.yml.tt

@@ -1,3 +1,7 @@
+# smtp:
+#   user_name: my-smtp-user
+#   password: my-smtp-password
+#
 # aws:
 #   access_key_id: 123
 #   secret_access_key: 345