Remove unused REST API endpoints

[nickdaugherty]

We never ended up utilizing this, so there's no reason to keep dead code laying around (especially code that allows creating users)

Worth noting that I checked for requests to this path, and there are only a handful of 404 GETs to it, so it is verified to be unused.

[nickdaugherty]

CI is busted with

E: Package 'libgcc-8-dev' has no installation candidate

Exited with code exit status 100

[nickdaugherty]

Finally got CI fixed.