FEATURE: channels can allow/disallow @all/@here mentions (#19317)

The settings tab of each category channel should now present the option to allow or disallow channel wide mentions: @here and @all.

When disallowed, using these mentions in the channel should have no effect.

plugins/chat/app/controllers/api/chat_channels_controller.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 CHAT_CHANNEL_EDITABLE_PARAMS = %i[name description]
-CATEGORY_CHAT_CHANNEL_EDITABLE_PARAMS = %i[auto_join_users]
+CATEGORY_CHAT_CHANNEL_EDITABLE_PARAMS = %i[auto_join_users allow_channel_wide_mentions]
 
 class Chat::Api::ChatChannelsController < Chat::Api
   def index

plugins/chat/app/models/chat_channel.rb

@@ -121,24 +121,25 @@ end
 #
 # Table name: chat_channels
 #
-#  id                      :bigint           not null, primary key
-#  chatable_id             :integer          not null
-#  deleted_at              :datetime
-#  deleted_by_id           :integer
-#  featured_in_category_id :integer
-#  delete_after_seconds    :integer
-#  chatable_type           :string           not null
-#  created_at              :datetime         not null
-#  updated_at              :datetime         not null
-#  name                    :string
-#  description             :text
-#  status                  :integer          default("open"), not null
-#  user_count              :integer          default(0), not null
-#  last_message_sent_at    :datetime         not null
-#  auto_join_users         :boolean          default(FALSE), not null
-#  user_count_stale        :boolean          default(FALSE), not null
-#  slug                    :string
-#  type                    :string
+#  id                           :bigint           not null, primary key
+#  chatable_id                  :integer          not null
+#  deleted_at                   :datetime
+#  deleted_by_id                :integer
+#  featured_in_category_id      :integer
+#  delete_after_seconds         :integer
+#  chatable_type                :string           not null
+#  created_at                   :datetime         not null
+#  updated_at                   :datetime         not null
+#  name                         :string
+#  description                  :text
+#  status                       :integer          default("open"), not null
+#  user_count                   :integer          default(0), not null
+#  last_message_sent_at         :datetime         not null
+#  auto_join_users              :boolean          default(FALSE), not null
+#  allow_channel_wide_mentions  :boolean          default(TRUE), not null
+#  user_count_stale             :boolean          default(FALSE), not null
+#  slug                         :string
+#  type                         :string
 #
 # Indexes
 #

plugins/chat/app/serializers/chat_channel_serializer.rb

@@ -3,6 +3,7 @@
 class ChatChannelSerializer < ApplicationSerializer
   attributes :id,
              :auto_join_users,
+             :allow_channel_wide_mentions,
              :chatable,
              :chatable_id,
              :chatable_type,