Ensure a SAML session is accepted by only one concurrent request and later attempts are rejected as invalid.
Add coverage for concurrent requests using the same session token so the single-use behavior stays enforced.
Signed-off-by: Utku Ozdemir <utku.ozdemir@siderolabs.com>
(cherry picked from commit ced79da6c032d2103803eb53343d0916cc957d2a)