https://github.com/spring-projects-experimental/spring-authorization-server/wiki/OAuth-2.0-Specifications

oauth2
https://tools.ietf.org/html/rfc6749
bearer token usage
https://tools.ietf.org/html/rfc6750
token introspection
https://tools.ietf.org/html/rfc7662
token revokation
https://tools.ietf.org/html/rfc7009
token exchange
https://tools.ietf.org/html/rfc8693
authorization server metadata
https://tools.ietf.org/html/rfc8414