Dynamic Auth Providers

[tylerstillwater]

We have many issues that are listed for adding auth providers. We should change Gomniauth to be dynamic in how it deals with this.

Instead of having an actual object per provider, we should have a generic provider class that uses a map of provider names to figure out how to make the request.

Each entry in the map would contain all the provider info necessary to talk to the provider, as well as another map defining the fields in the response that are necessary for building our internal user object.

If this was implemented, adding a new provider would be as easy as simply adding a new entry to the default provider data map.