fix: un-assign agent from conversation after removal (#5417)

Unassign agents from the conversation when they are removed from the account.

Fixes: #4555

app/services/agents/destroy_service.rb

@@ -6,6 +6,7 @@ class Agents::DestroyService
       destroy_notification_setting
       remove_user_from_teams
       remove_user_from_inboxes
+      unassign_conversations
     end
   end
 
@@ -27,4 +28,8 @@ class Agents::DestroyService
     setting = user.notification_settings.find_by(account_id: account.id)
     setting&.destroy!
   end
+
+  def unassign_conversations
+    user.assigned_conversations.where(account: account).find_each(&:update_assignee)
+  end
 end