Migrate off of gorilla/mux as it is archived

[mpuckett159]

As has been pretty publicly announced the gorilla project is basically archived at this point, no longer to be supported. We need to identify an alternative to use.

Or pick up maintenance of it that'd be pretty sick but I doubt any of us have the capacity for that unfortunately.

[AetherUnbound]

I think I'd really like to try migrating this to FastAPI - it'd be a good learning opportunity and python would be consistent with the rest of our services!