I have looked into various OAuth2 java libraries (spring-security-oauth, cxf, scribe, google-oauth-java-client) and could not find anything out there that supports the Mac token type as described here: https://datatracker.ietf.org/doc/html/draft-ietf-oauth-v2-http-mac-01
All of them support the Bearer token type by default and nothing else. Is there any particular reason why this token type is not supported at all?