chore: Add controllers for conversation participants (#6462)

Co-authored-by: Aswin Dev P.S <aswindevps@gmail.com>
Co-authored-by: Sojan Jose <sojan@chatwoot.com>

app/models/concerns/assignment_handler.rb

@@ -4,7 +4,7 @@ module AssignmentHandler
 
   included do
     before_save :ensure_assignee_is_from_team
-    after_commit :notify_assignment_change, :process_assignment_activities
+    after_commit :notify_assignment_change, :process_assignment_changes
   end
 
   private
@@ -36,6 +36,11 @@ module AssignmentHandler
     end
   end
 
+  def process_assignment_changes
+    process_assignment_activities
+    process_participant_assignment
+  end
+
   def process_assignment_activities
     user_name = Current.user.name if Current.user.present?
     if saved_change_to_team_id?
@@ -44,4 +49,10 @@ module AssignmentHandler
       create_assignee_change_activity(user_name)
     end
   end
+
+  def process_participant_assignment
+    return unless saved_change_to_assignee_id? && assignee_id.present?
+
+    conversation_participants.find_or_create_by!(user_id: assignee_id)
+  end
 end