OAuth: Use the attached external session data in OAuthToken and OAuthTokenSync (#96655)

* wip

* wip + tests

* wip

* wip opt2

* Use authn.Identity struct's SessionToken

* Merge fixes

* Handle disabling the feature flag correctly

* Fix test

* Cleanup

* Remove HasOAuthEntry from the OAuthTokenService interface

* Remove unused function

pkg/api/pluginproxy/ds_proxy_test.go

@@ -32,7 +32,9 @@ import (
 	pluginfakes "github.com/grafana/grafana/pkg/plugins/manager/fakes"
 	"github.com/grafana/grafana/pkg/services/accesscontrol/acimpl"
 	"github.com/grafana/grafana/pkg/services/accesscontrol/actest"
+	"github.com/grafana/grafana/pkg/services/auth"
 	"github.com/grafana/grafana/pkg/services/authz/zanzana"
+	"github.com/grafana/grafana/pkg/services/contexthandler/ctxkey"
 	contextmodel "github.com/grafana/grafana/pkg/services/contexthandler/model"
 	"github.com/grafana/grafana/pkg/services/datasources"
 	datasourceservice "github.com/grafana/grafana/pkg/services/datasources/service"
@@ -557,7 +559,7 @@ func TestDataSourceProxy_routeRule(t *testing.T) {
 		var routes []*plugins.Route
 		proxy, err := setupDSProxyTest(t, ctx, ds, routes, "/path/to/folder/", func(proxy *DataSourceProxy) {
 			proxy.oAuthTokenService = &oauthtokentest.MockOauthTokenService{
-				GetCurrentOauthTokenFunc: func(_ context.Context, _ identity.Requester) *oauth2.Token {
+				GetCurrentOauthTokenFunc: func(_ context.Context, _ identity.Requester, _ *auth.UserToken) *oauth2.Token {
 					return (&oauth2.Token{
 						AccessToken:  "testtoken",
 						RefreshToken: "testrefreshtoken",
@@ -573,6 +575,7 @@ func TestDataSourceProxy_routeRule(t *testing.T) {
 		require.NoError(t, err)
 
 		req, err = http.NewRequest(http.MethodGet, "http://grafana.com/sub", nil)
+		req = req.WithContext(context.WithValue(req.Context(), ctxkey.Key{}, &contextmodel.ReqContext{UserToken: nil}))
 		require.NoError(t, err)
 
 		proxy.director(req)