Set up some basic authentication handling with JWT

[jupiter007]

We want to set up a simple "username, password" authentication initially with JWT. This will allow us to test some basic authentication and to set up some infrastructure for it.

[jupiter007]

I added some initial code to help us run some initial tests and think about infrastructure:

https://github.com/CDLUC3/dmsp_backend_prototype/tree/feature/simple-authentication