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

https://www.oauth.com/oauth2-servers/token-introspection-endpoint/

oauth2
The OAuth 2.0 Authorization Framework
    https://datatracker.ietf.org/doc/html/rfc6749
    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