[keycloak-dev] Passing login_hint up to IdP when using kc_idp_hint

[Peter Chamberlin]

Hi Keycloak team,

I'm working on a system which uses Keycloak as a broker to both OIDC and
SAML2.0 IdPs. We are using `kc_idp_hint` for every request and Keycloak is
never exposed to the user. The system uses OIDC to connect to Keycloak.

We would like to pass a `login_hint` or `subject` upstream to  IdPs
(depending if it's OIDC or SAML) as we expect to know the user's IdP user
name, but this does not work out of the box. I can't see anything in the
documentation that would enable it.

Is it possible? If so how?

Many thanks for any help or pointers you can give.

Peter Chamberlin