Removed auth path

[arsa-dev]

Newer versions of keycloak now have different hostnames for admin console and frontend endpoints (see https://www.keycloak.org/server/hostname), so auth path in url is now deprecated and shouldn't be hardcoded at package if we want to use it. Anyway if someone is still using an older version of keycloak he can simply configure the url with /auth at the end so he can also use the library.