Add mailer previews for Devise mailer (#10890)

* Add mailer previews for Devise mailer

Issue #10575

* Don't use short module syntax, move file to correct place
Issue #10575

* Fix Devise::Mailer previews

* Separate DeviseInvitable mailers

Co-authored-by: rhymes <rhymes@hey.com>

spec/mailers/previews/devise/mailer_preview.rb

@@ -0,0 +1,24 @@
+# Preview all emails at http://localhost:3000/rails/mailers/devise/mailer
+module Devise
+  class MailerPreview < ActionMailer::Preview
+    def confirmation_instructions
+      Devise::Mailer.confirmation_instructions(User.last, "faketoken")
+    end
+
+    def email_changed
+      Devise::Mailer.email_changed(User.last)
+    end
+
+    def password_change
+      Devise::Mailer.password_change(User.last)
+    end
+
+    def reset_password_instructions
+      Devise::Mailer.reset_password_instructions(User.last, "faketoken")
+    end
+
+    def unlock_instructions
+      Devise::Mailer.unlock_instructions(User.last, "faketoken")
+    end
+  end
+end

spec/mailers/previews/devise_invitable/mailer_preview.rb

@@ -0,0 +1,8 @@
+# Preview all emails at http://localhost:3000/rails/mailers/devise/mailer
+module DeviseInvitable
+  class MailerPreview < ActionMailer::Preview
+    def invitation_instructions
+      Devise::Mailer.invitation_instructions(User.last, "faketoken")
+    end
+  end
+end