Issue: Message Processing Failure - User Leaves Mid-Ticket

[bberka]

Currently, if a user creates a Modmail ticket and then leaves the Discord server, any further messages sent by either the user or moderators cannot be processed. The Discord API returns a 403 (Forbidden) error when the bot attempts to interact with the user, leading to an unhandled exception.

Impact:

• The ticket becomes unusable.
• Moderators are unable to communicate with the user.
• Unhandled exceptions can destabilize the bot.

Proposed Solutions (Choose One or Both):

1. Automatic Closure:

   • Implement a mechanism to automatically close tickets when the user leaves the server.
   • Consider making this behavior a configurable option (enabled by default).

2. Informational Message:

   • When a user leaves the server with an active ticket, send a message to the ticket channel stating that the user is no longer present and further messages will not be processed.

A solution is needed to gracefully handle this scenario.