FEATURE: limits post created edited trigger to a group (#31523)

This commit allows admins to limit the post created/edited trigger
execution to a specific post user group.

It's for example useful if you want to auto tag all the topics created
by member of a specific group.

plugins/automation/lib/discourse_automation/event_handlers.rb

@@ -65,6 +65,9 @@ module DiscourseAutomation
             next if ignore_group_members && post.user.in_any_groups?(restricted_group_ids)
           end
 
+          user_group = automation.trigger_field("restricted_user_group")["value"]
+          next if user_group && !post.user.in_any_groups?([user_group])
+
           ignore_automated = automation.trigger_field("ignore_automated")
           next if ignore_automated["value"] && post.incoming_email&.is_auto_generated?