Update used API endpoints to the current spec

Updates the key upload endpoint and moves it into it's
own module as a constant.

Closes #24
2 jobs for update-endpoints in 4 minutes and 33 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Build
passed run-build #278278

00:02:18

 
  Lint
passed run-lint #278279

00:02:15