register several endpoints of a kind

[azmeuk]

I am currently tackling #427 and I realize it would be easier for me if one could register several endpoints of a kind. For instance one JWTAccessTokenIntrospectionEndpoint that would read the introspection data from the JWT access token, and a regular IntrospectionEndpoint for the other kind of tokens.

With this patch, if JWTAccessTokenIntrospectionEndpoint would meet a plain-text access token, it would raise a ContinueIteration exception and pass to the IntrospectionEndpoint. Same if the token_hint is a refresh token for instance (RFC9068 is only about access tokens).

This would also help for the revokation endpoint.

What do you think?

[azmeuk]

An alternative to this would be to implement register_introspection_endpoint and register_revokation_endpoint with an optional token_type parameter, in the fashion of register_token_generator. However that would be a breaking change.
What do you think @lepture?

[lepture]

@azmeuk I think your implementation looks good. Would you like to add endpoints in this branch, or let me merge it at first?

[azmeuk]

We can merge this now so the branch diff will be easier to read.

[lepture]

Merged.