IDforwarding: forward signed id to plugins (#75651)

* Plugins: Add client middlware that forwards the signed grafana id token if present

* DsProxy: Set grafana id header if id token exists

* Add util function to apply id token to header

* Only add id forwarding middleware if feature toggle is enabled

* Add feature toggles to ds proxy and check if id forwarding is enabled

* Clean up test setup

* Change to use backend.ForwardHTTPHeaders interface

* PluginProxy: Forward signed identity when feature toggle is enabled

* PluginProxy: forrward signed id header

pkg/services/pluginsintegration/clientmiddleware/forward_id_middleware_test.go

@@ -0,0 +1,50 @@
+package clientmiddleware
+
+import (
+	"context"
+	"net/http"
+	"testing"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
+	"github.com/grafana/grafana/pkg/web"
+	"github.com/stretchr/testify/require"
+
+	"github.com/grafana/grafana/pkg/plugins/manager/client/clienttest"
+	"github.com/grafana/grafana/pkg/services/contexthandler/ctxkey"
+	contextmodel "github.com/grafana/grafana/pkg/services/contexthandler/model"
+	"github.com/grafana/grafana/pkg/services/user"
+)
+
+func TestForwardIDMiddleware(t *testing.T) {
+	t.Run("Should set forwarded id header if present", func(t *testing.T) {
+		cdt := clienttest.NewClientDecoratorTest(t, clienttest.WithMiddlewares(NewForwardIDMiddleware()))
+
+		ctx := context.WithValue(context.Background(), ctxkey.Key{}, &contextmodel.ReqContext{
+			Context:      &web.Context{Req: &http.Request{}},
+			SignedInUser: &user.SignedInUser{IDToken: "some-token"},
+		})
+
+		err := cdt.Decorator.CallResource(ctx, &backend.CallResourceRequest{
+			PluginContext: backend.PluginContext{},
+		}, nopCallResourceSender)
+		require.NoError(t, err)
+
+		require.Equal(t, "some-token", cdt.CallResourceReq.Headers[forwardIDHeaderName][0])
+	})
+
+	t.Run("Should not set forwarded id header if not present", func(t *testing.T) {
+		cdt := clienttest.NewClientDecoratorTest(t, clienttest.WithMiddlewares(NewForwardIDMiddleware()))
+
+		ctx := context.WithValue(context.Background(), ctxkey.Key{}, &contextmodel.ReqContext{
+			Context:      &web.Context{Req: &http.Request{}},
+			SignedInUser: &user.SignedInUser{},
+		})
+
+		err := cdt.Decorator.CallResource(ctx, &backend.CallResourceRequest{
+			PluginContext: backend.PluginContext{},
+		}, nopCallResourceSender)
+		require.NoError(t, err)
+
+		require.Len(t, cdt.CallResourceReq.Headers[forwardIDHeaderName], 0)
+	})
+}