The grey color has been used to show that's optional, and a loop arrow to represent that multiple hooks can be stacked. We can distinctly see three kind of hooks: 1) pre/post+token/auth 2) generate access/refresh tokens 3) code/token modifiers. Also, I have added the optional RequestValidator.rotate_refresh_token callback.

A new RequestValidator `fill_id_token` has been introduced to replace `get_id_token`. It aims to have the bare minimum amount of fields to complete a full OIDC id_token support. `get_id_token` is still valid but optional, and if it is implemented, `fill_id_token` will not be called. The current `fill_id_token` came with full support of `aud`, `iat`, `nonce`, `at_hash` and `c_hash`. More could come in the future e.g. `auth_time`, ...