Enable more frozen string in app/models/**/*.rb

Partially addresses #47424.

app/models/diff_viewer/image.rb

+# frozen_string_literal: true
+
 module DiffViewer
   class Image < Base
     include Rich

app/models/diff_viewer/mode_changed.rb

+# frozen_string_literal: true
+
 module DiffViewer
   class ModeChanged < Base
     include Simple

app/models/diff_viewer/no_preview.rb

+# frozen_string_literal: true
+
 module DiffViewer
   class NoPreview < Base
     include Simple

app/models/diff_viewer/not_diffable.rb

+# frozen_string_literal: true
+
 module DiffViewer
   class NotDiffable < Base
     include Simple

app/models/diff_viewer/renamed.rb

+# frozen_string_literal: true
+
 module DiffViewer
   class Renamed < Base
     include Simple

app/models/diff_viewer/rich.rb

+# frozen_string_literal: true
+
 module DiffViewer
   module Rich
     extend ActiveSupport::Concern

app/models/diff_viewer/server_side.rb

+# frozen_string_literal: true
+
 module DiffViewer
   module ServerSide
     extend ActiveSupport::Concern

app/models/diff_viewer/simple.rb

+# frozen_string_literal: true
+
 module DiffViewer
   module Simple
     extend ActiveSupport::Concern

app/models/diff_viewer/static.rb

+# frozen_string_literal: true
+
 module DiffViewer
   module Static
     extend ActiveSupport::Concern

app/models/diff_viewer/text.rb

+# frozen_string_literal: true
+
 module DiffViewer
   class Text < Base
     include Simple

app/models/hooks/project_hook.rb

+# frozen_string_literal: true
+
 class ProjectHook < WebHook
   include TriggerableHooks

app/models/hooks/service_hook.rb

+# frozen_string_literal: true
+
 class ServiceHook < WebHook
   belongs_to :service
   validates :service, presence: true

app/models/hooks/system_hook.rb

+# frozen_string_literal: true
+
 class SystemHook < WebHook
   include TriggerableHooks

app/models/hooks/web_hook.rb

+# frozen_string_literal: true
+
 class WebHook < ActiveRecord::Base
   include Sortable

app/models/hooks/web_hook_log.rb

+# frozen_string_literal: true
+
 class WebHookLog < ActiveRecord::Base
   belongs_to :web_hook

app/models/issue/metrics.rb

+# frozen_string_literal: true
+
 class Issue::Metrics < ActiveRecord::Base
   belongs_to :issue

app/models/members/group_member.rb

+# frozen_string_literal: true
+
 class GroupMember < Member
   SOURCE_TYPE = 'Namespace'.freeze

app/models/members/project_member.rb

+# frozen_string_literal: true
+
 class ProjectMember < Member
   SOURCE_TYPE = 'Project'.freeze

app/models/merge_request/metrics.rb

+# frozen_string_literal: true
+
 class MergeRequest::Metrics < ActiveRecord::Base
   belongs_to :merge_request
   belongs_to :pipeline, class_name: 'Ci::Pipeline', foreign_key: :pipeline_id

app/models/network/commit.rb

+# frozen_string_literal: true
+
 module Network
   class Commit
     include ActionView::Helpers::TagHelper