DEV: add plugin hooks for silence message parameters (#10538)

DEV: add plugin hooks for silence message parameters

Allows plugins to add, and update extra silence message params for custom
i18n vars

Allows plugins to override system messages via `message_title` and
`message_raw` parameters. We can later expose these params where necessary via event
hooks. Expose the parameter for the on user_silenced trigger.

app/services/user_silencer.rb

@@ -36,7 +36,6 @@ class UserSilencer
         ).format
 
         context = "#{message_type}: '#{post.topic&.title rescue ''}' #{@opts[:reason]}"
-        SystemMessage.create(@user, message_type)
 
         if @by_user
           log_params = { context: context, details: details }
@@ -48,6 +47,7 @@ class UserSilencer
           )
         end
 
+        silence_message_params = {}
         DiscourseEvent.trigger(
           :user_silenced,
           user: @user,
@@ -57,8 +57,11 @@ class UserSilencer
           user_history: @user_history,
           post_id: @opts[:post_id],
           silenced_till: @user.silenced_till,
-          silenced_at: DateTime.now
+          silenced_at: DateTime.now,
+          silence_message_params: silence_message_params
         )
+
+        SystemMessage.create(@user, message_type, silence_message_params)
         true
       end
     else