title: Identity Sever 4 Persisted Grants not being used
body: <p>I've implemented IPersistedGrantStore, and defined a Client that has properties RequireConsent and AllowRememberConsent set to true. I've also removed offline access scope from that client as I've read somewhere that Consent is always forced if offline access scope is requested, as per OAuth specification.
  When I go to the login screen for the first time, I'm presented with consent view, click allow and remember my decision, I can see the record in DB table PersistedGrants being added with type user_consent. Next time I try to login, that record is fetched from database by my implementation of IPersistedGrantStore, but the consent view is still presented. If I then click allow again, DB throws an exception because IS4 is trying to insert another PersistedGrant record with the same key.</p>
  
  <p>Did I overlook certain setting that would make it behave as expected?
  PS. I've implemented all major stores and everything is kept in SQL Server db, not using any of those InMemory stores.</p>