Request: Follow Semantic Versioning for Future Releases

[MichaelAndish]

Hi team,
I noticed that the latest release introduced breaking changes that aren’t backward compatible, which caused issues in our app.

I'm talking about this PR: https://github.com/go-oauth2/oauth2/pull/279/files

token, oauth2AccessTokenExists := a.authServer.AccessTokenResolveHandler(r) 

Since these changes break existing functionality, they should ideally be released as a major version instead of a minor or patch. Could you please consider following semantic versioning more strictly in future releases to help avoid unexpected breaks?

Thanks a lot for your work on this package! 🙏