Create Token Auth Server for Examples/Simple Deploys

### Improvement

Our chosen approach to authentication in [this](https://github.com/azavea/franklin/blob/master/docs/0004-make-authentication-configurable-at-server-startup.md) ADR requires a separate service that handles authentication. We should provide a sample service that can does opaque token authentication.

### Acceptance
- [ ] New subproject with authentication server - this will have its own migrations and commands for invoking it; can likely have the application module be a dependency since that's where the auth datamodel will likely live
- [ ] New jar/docker container in Quay (`franklin-auth`) that can be referenced/used in samples in the Franklin repository
- [ ] Published docker containers in Quay that can be referenced/used in samples in the Franklin repository
- [ ] Connects to a database that stores valid tokens with migrations to add table for tokens
- [ ] Will need commands for starting the server and running migrations

Start by reading the authentication ADR at docs/0004-make-authentication-configurable-at-server-startup.md and reviewing the repository's application module. Define a new authentication-server subproject with database migrations, startup and migration commands, and a Docker image published as franklin-auth; done means it can store and validate opaque tokens and be referenced by Franklin examples.

Written by the indexing model from the issue text.