WebSession: drop OAUTH1 support

* Drops support for OAUTH1 based authentication in favor of
  established OAUTH2.
  (closes #2170) (pr #2241)

Signed-off-by: Samuele Kaplun <samuele.kaplun@cern.ch>
Reviewed-by: Tibor Simko <tibor.simko@cern.ch>
Reviewed-by: Jiri Kuncar <jiri.kuncar@cern.ch>