[keycloak-dev] Adding a custom field to OIDC/SAML provider setup

[John Eckhart]

I would like to add a custom field/property/attribute to an OIDC or SAML
provider and I'm looking for a few pointers.

The use-case is to have many identity providers configured in Keycloak and
prompt the user to enter their email address to determine which IdP to
redirect the user. Each IdP would have one email suffix that it provides
logins for (this would be the custom field). This is a similar flow to
Microsoft's Office 365 and OpsGenie's federated login.

Although this could be implemented outside of Keycloak, ideally we could
contain this as a custom Rest API added to KC while extending a theme and
SPI reusing as much as possible inside Keycloak.

Any thoughts/tips are much appreciated.