[keycloak-user] Using email attribute in SAML identity brokering

Hi, We have a few clients integrated with Keycloak relam, using email address as the user identifier. Now we wish to integrate KeyCloak with external IdP using its identity brokering capabilities based on SAML. The problem is, the user identifier in the external IdP is not the email address but some other username. We are able to get the email as an attribute in the SAML assertion coming into KeyCloak, but the missing part is mapping the email attribute to the user identifier in KeyCloak - how do we do that? Thanks! The information contained in this message is proprietary to the sender, protected from disclosure, and may be privileged. The information is intended to be conveyed only to the designated recipient(s) of the message. If the reader of this message is not the intended recipient, you are hereby notified that any dissemination, use, distribution or copying of this communication is strictly prohibited and may be unlawful. If you have received this communication in error, please notify us immediately by replying to the message and deleting it from your computer. Thank you.