Only allow one non-archived sitting thread per user at a given time

[ajar]

Suggested fix without thinking too hard about it...

• When the button is pressed to create a session, assign the @needs-help role first.
• When a request is received by a user with that role, short-circuit normal action logic and...
• ... instead, create an ephemeral message that pings the user inside of the active thread.
• When all sessions are archived, remove the @needs-help role, restoring normal functionality.

[ajar]

Could make an ephemeral message for their eyes only underneath the main part as well which links them to the thread...

[LunaUrsa]

So this was already coded i just forgot: https://github.com/TripSit/tripsit-discord-bot/blob/main/src/commands/guild/tripsitme.js#L55