auth/backends: Fix cache TTL computation for OIDC profile
The cache TTL for storing an OIDC profile must be computed from the
access token renewal date (iat
field in decoded token) and not from
the OIDC session opening date (auth_time
field in decoded token).
Previous implementation was computing a negative TTL (clamped to 0) once the first issued refresh token was expired and thus the authentication process was then failing.
Migrated from D5269 (view on Phabricator)