Logically split auth API from the rest of the map ingestion API

[davenquinn]

If this codebase is going to be a general-purpose API v3 for Macrostrat, we need to keep things separate by functional silo, to facilitate easier independent development in the future.

The security module, in particular, needs to be something that can easily be brought to bear in many contexts. Eventually, this could look like pulling it out into its own Python module (maybe in the UW-Macrostrat/python-libraries repo). Or, this could be its own microservice. A first step would be separating it from the other parts of the application code here.

[davenquinn]

Alternatively, we could recast this API as a map-ingestion-specific service.