Remove padding to fix compatibility with new keycloak version
From https://cern.service-now.com/service-portal?id=outage&n=OTG0074619
This new version includes changes in PKCE validation which impact Device Authorization Grant. These changes remain compliant with standards, but our previous version of "auth-get-user-token" is no longer compatible. We advise updating this tool and checking compatibility of any clients using "device flow" with PKCE (see also: https://github.com/keycloak/keycloak/issues/15739).
the issue https://github.com/keycloak/keycloak/issues/15739 suggests removing =
padding at the end of the b64 encoded string