Send DM to user on Form Submission

[janine9vn]

Description

Send a DM to a user after they have submitted a form. This may, or may not, include snekbox results if there is a code evaluation component.

Justification

Sometimes it is nice if users get notified about their submission. Code Jam participants and Esoteric Challenge participants should also get notified/a role added if snekbox evaluation goes correctly.

Implementation

This should be implemented as a Starlette background task. This has to ignore/handle all errors (DMs closed, not in server, etc.). First, this has to make sure is there already a DM channel open with a user. If there isn't, this should open it. After this send endpoint can be used.

The interface with the Discord API for the DM and/or role addition is via an HTTP Request to the Discord API. The backend already has access to a bot token to use (Python's token specifically).