Enable frozen string in app/models/*.rb

Partially addresses #47424.

app/models/project_team.rb

+# frozen_string_literal: true
+
 class ProjectTeam
   include BulkMemberAccessLoad

app/models/protectable_dropdown.rb

+# frozen_string_literal: true
+
 class ProtectableDropdown
   REF_TYPES = %i[branches tags].freeze

app/models/protected_branch.rb

+# frozen_string_literal: true
+
 class ProtectedBranch < ActiveRecord::Base
   include Gitlab::ShellAdapter
   include ProtectedRef

app/models/protected_ref_matcher.rb

+# frozen_string_literal: true
+
 class ProtectedRefMatcher
   def initialize(protected_ref)
     @protected_ref = protected_ref

app/models/protected_tag.rb

+# frozen_string_literal: true
+
 class ProtectedTag < ActiveRecord::Base
   include Gitlab::ShellAdapter
   include ProtectedRef

app/models/push_event.rb

+# frozen_string_literal: true
+
 class PushEvent < Event
   # This validation exists so we can't accidentally use PushEvent with a
   # different "action" value.

app/models/push_event_payload.rb

+# frozen_string_literal: true
+
 class PushEventPayload < ActiveRecord::Base
   include ShaAttribute

app/models/readme_blob.rb

+# frozen_string_literal: true
+
 class ReadmeBlob < SimpleDelegator
   attr_reader :repository

app/models/redirect_route.rb

+# frozen_string_literal: true
+
 class RedirectRoute < ActiveRecord::Base
   belongs_to :source, polymorphic: true # rubocop:disable Cop/PolymorphicAssociations

app/models/release.rb

+# frozen_string_literal: true
+
 class Release < ActiveRecord::Base
   include CacheMarkdownField

app/models/remote_mirror.rb

+# frozen_string_literal: true
+
 class RemoteMirror < ActiveRecord::Base
   include AfterCommitQueue

app/models/repository.rb

+# frozen_string_literal: true
+
 require 'securerandom'
 class Repository

app/models/route.rb

+# frozen_string_literal: true
+
 class Route < ActiveRecord::Base
   include CaseSensitivity

app/models/security_event.rb

+# frozen_string_literal: true
+
 class SecurityEvent < AuditEvent
 end

app/models/sent_notification.rb

+# frozen_string_literal: true
+
 class SentNotification < ActiveRecord::Base
   serialize :position, Gitlab::Diff::Position # rubocop:disable Cop/ActiveRecordSerialize

app/models/service.rb

+# frozen_string_literal: true
+
 # To add new service you should build a class inherited from Service
 # and implement a set of methods
 class Service < ActiveRecord::Base

app/models/snippet.rb

+# frozen_string_literal: true
+
 class Snippet < ActiveRecord::Base
   include Gitlab::VisibilityLevel
   include CacheMarkdownField

app/models/snippet_blob.rb

+# frozen_string_literal: true
+
 class SnippetBlob
   include BlobLike

app/models/spam_log.rb

+# frozen_string_literal: true
+
 class SpamLog < ActiveRecord::Base
   belongs_to :user

app/models/subscription.rb

+# frozen_string_literal: true
+
 class Subscription < ActiveRecord::Base
   belongs_to :user
   belongs_to :project