django/models: Add new fields and dict profile getter to OIDCUser
Add fields "expires_in" and "refresh_expires_in" to OIDCUser model storing the validity times for access and refresh tokens.
Add oidc_profile method to get the OpenID Connect profile associated to the user as a dictionary.
Update and simplify tests for OIDCUser model.
Related to swh-web#3150 (closed)
Migrated from D5325 (view on Phabricator)