Plugins: Forward user header (X-Grafana-User) in backend plugin requests (#58646)

Grafana would forward the X-Grafana-User header to backend plugin request when 
dataproxy.send_user_header is enabled. In addition, X-Grafana-User will be automatically
forwarded in outgoing HTTP requests for core/builtin HTTP datasources. 
Use grafana-plugin-sdk-go v0.147.0.

Fixes #47734

Co-authored-by: Will Browne <wbrowne@users.noreply.github.com>

pkg/services/pluginsintegration/clientmiddleware/user_header_middleware.go

@@ -0,0 +1,103 @@
+package clientmiddleware
+
+import (
+	"context"
+	"net/http"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
+	sdkhttpclient "github.com/grafana/grafana-plugin-sdk-go/backend/httpclient"
+	"github.com/grafana/grafana/pkg/infra/httpclient/httpclientprovider"
+	"github.com/grafana/grafana/pkg/plugins"
+	"github.com/grafana/grafana/pkg/services/contexthandler"
+	"github.com/grafana/grafana/pkg/util/proxyutil"
+)
+
+// NewUserHeaderMiddleware creates a new plugins.ClientMiddleware that will
+// populate the X-Grafana-User header on outgoing plugins.Client and HTTP
+// requests.
+func NewUserHeaderMiddleware() plugins.ClientMiddleware {
+	return plugins.ClientMiddlewareFunc(func(next plugins.Client) plugins.Client {
+		return &UserHeaderMiddleware{
+			next: next,
+		}
+	})
+}
+
+type UserHeaderMiddleware struct {
+	next plugins.Client
+}
+
+func (m *UserHeaderMiddleware) applyToken(ctx context.Context, pCtx backend.PluginContext, h backend.ForwardHTTPHeaders) context.Context {
+	reqCtx := contexthandler.FromContext(ctx)
+	// if no HTTP request context skip middleware
+	if h == nil || reqCtx == nil || reqCtx.Req == nil || reqCtx.SignedInUser == nil {
+		return ctx
+	}
+
+	h.DeleteHTTPHeader(proxyutil.UserHeaderName)
+	if !reqCtx.IsAnonymous {
+		h.SetHTTPHeader(proxyutil.UserHeaderName, reqCtx.Login)
+	}
+
+	middlewares := []sdkhttpclient.Middleware{}
+
+	if !reqCtx.IsAnonymous {
+		httpHeaders := http.Header{
+			proxyutil.UserHeaderName: []string{reqCtx.Login},
+		}
+
+		middlewares = append(middlewares, httpclientprovider.SetHeadersMiddleware(httpHeaders))
+	} else {
+		middlewares = append(middlewares, httpclientprovider.DeleteHeadersMiddleware(proxyutil.UserHeaderName))
+	}
+
+	ctx = sdkhttpclient.WithContextualMiddleware(ctx, middlewares...)
+
+	return ctx
+}
+
+func (m *UserHeaderMiddleware) QueryData(ctx context.Context, req *backend.QueryDataRequest) (*backend.QueryDataResponse, error) {
+	if req == nil {
+		return m.next.QueryData(ctx, req)
+	}
+
+	ctx = m.applyToken(ctx, req.PluginContext, req)
+
+	return m.next.QueryData(ctx, req)
+}
+
+func (m *UserHeaderMiddleware) CallResource(ctx context.Context, req *backend.CallResourceRequest, sender backend.CallResourceResponseSender) error {
+	if req == nil {
+		return m.next.CallResource(ctx, req, sender)
+	}
+
+	ctx = m.applyToken(ctx, req.PluginContext, req)
+
+	return m.next.CallResource(ctx, req, sender)
+}
+
+func (m *UserHeaderMiddleware) CheckHealth(ctx context.Context, req *backend.CheckHealthRequest) (*backend.CheckHealthResult, error) {
+	if req == nil {
+		return m.next.CheckHealth(ctx, req)
+	}
+
+	ctx = m.applyToken(ctx, req.PluginContext, req)
+
+	return m.next.CheckHealth(ctx, req)
+}
+
+func (m *UserHeaderMiddleware) CollectMetrics(ctx context.Context, req *backend.CollectMetricsRequest) (*backend.CollectMetricsResult, error) {
+	return m.next.CollectMetrics(ctx, req)
+}
+
+func (m *UserHeaderMiddleware) SubscribeStream(ctx context.Context, req *backend.SubscribeStreamRequest) (*backend.SubscribeStreamResponse, error) {
+	return m.next.SubscribeStream(ctx, req)
+}
+
+func (m *UserHeaderMiddleware) PublishStream(ctx context.Context, req *backend.PublishStreamRequest) (*backend.PublishStreamResponse, error) {
+	return m.next.PublishStream(ctx, req)
+}
+
+func (m *UserHeaderMiddleware) RunStream(ctx context.Context, req *backend.RunStreamRequest, sender *backend.StreamSender) error {
+	return m.next.RunStream(ctx, req, sender)
+}