How can I obtain a bearer token from keycloak without using the direct access grant (http://keycloak.github.io/docs/userguide/keycloak-server/html/direct-access-grants.html).

I have configured a SAML Identity Broker in Keycloak which handles the login for my realm. As a result I do not have a username/password combination to POST it to:

/{keycloak-root}/realms/{realm-name}/protocol/openid-connect/token

How would I obtain a bearer token in this situation?