A simple Authorization Server sample based off of the Legacy
Authorization Server project, spring-security-oauth2.
This project is mostly useful as a utility for other samples whose
usage would be clearer if an Authorization Server were introduced.
Note that this server is a barebones OAuth 2.0 Authorization Server
configuration, but is still useful for understanding how to set up an
Authorization Server using spring-security-oauth2.
Fixes: gh-5833
