AuthN: fetch final state of signed in user (#62854)

* AuthN: add a hook we can use to fetch final state of user

pkg/services/authn/authnimpl/sync/fetch_user_sync_test.go

@@ -0,0 +1,40 @@
+package sync
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/grafana/grafana/pkg/services/authn"
+)
+
+func TestFetchUserSync_FetchSyncedUserHook(t *testing.T) {
+	type testCase struct {
+		desc        string
+		req         *authn.Request
+		identity    *authn.Identity
+		expectedErr error
+	}
+
+	tests := []testCase{
+		{
+			desc:     "should skip hook when flag is not enabled",
+			req:      &authn.Request{},
+			identity: &authn.Identity{ClientParams: authn.ClientParams{FetchSyncedUser: false}},
+		},
+		{
+			desc:     "should skip hook when identity is not a user",
+			req:      &authn.Request{},
+			identity: &authn.Identity{ID: "apikey:1", ClientParams: authn.ClientParams{FetchSyncedUser: true}},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			s := ProvideFetchUserSync(nil)
+			err := s.FetchSyncedUserHook(context.Background(), tt.identity, tt.req)
+			require.ErrorIs(t, err, tt.expectedErr)
+		})
+	}
+}