Support for authentication middleware (eg: oauth2-proxy) ?

Hello,

probably best way to explain is to have a look at the Architecture diagram of oauth2-proxy and see the image on the right: "Oauth 2 proxy as authentication middleware", although the feature is not exclusive to oauth2-proxy.

Both nginx and Caddy support this concept. Nginx calls it auth_request; Caddy calls it forward_auth.

Only mention of this feature I found is a ticket from 2016: https://github.com/fabiolb/fabio/issues/64.

Are there any plans to support this feature? If no, I can totally understand :-)

Thanks!

EDIT: adding a copy of the diagram here: