AuthN: Add session client (#60894)

* add basic session client

* populate UserToken in ReqContext

* token rotation as a post auth hook

* fixed in context handler

* add session token rotation

* add session token tests

* use namespacedID constructor

pkg/services/authn/authnimpl/usersync/usersync_test.go

@@ -430,7 +430,7 @@ func TestUserSync_SyncUser(t *testing.T) {
 				quotaService:    tt.fields.quotaService,
 				log:             tt.fields.log,
 			}
-			err := s.SyncUser(tt.args.ctx, tt.args.clientParams, tt.args.id)
+			err := s.SyncUser(tt.args.ctx, tt.args.clientParams, tt.args.id, nil)
 			if tt.wantErr {
 				require.Error(t, err)
 				return