Plugins: Automatically forward plugin request HTTP headers in outgoing HTTP requests (#60417)

Automatically forward core plugin request HTTP headers in outgoing HTTP requests. 
Core datasource plugin authors don't have to specifically handle forwarding of HTTP 
headers, e.g. do not have to "hardcode" the header-names in the datasource plugin, 
if not having custom needs.

Fixes #57065

pkg/services/pluginsintegration/clientmiddleware/clear_auth_headers_middleware.go

@@ -4,8 +4,6 @@ import (
 	"context"
 
 	"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"
 )
@@ -25,19 +23,19 @@ type ClearAuthHeadersMiddleware struct {
 	next plugins.Client
 }
 
-func (m *ClearAuthHeadersMiddleware) clearHeaders(ctx context.Context, pCtx backend.PluginContext, req interface{}) context.Context {
+func (m *ClearAuthHeadersMiddleware) clearHeaders(ctx context.Context, h backend.ForwardHTTPHeaders) {
 	reqCtx := contexthandler.FromContext(ctx)
 	// if no HTTP request context skip middleware
-	if req == nil || reqCtx == nil || reqCtx.Req == nil || reqCtx.SignedInUser == nil {
-		return ctx
+	if h == nil || reqCtx == nil || reqCtx.Req == nil || reqCtx.SignedInUser == nil {
+		return
 	}
 
 	list := contexthandler.AuthHTTPHeaderListFromContext(ctx)
 	if list != nil {
-		ctx = sdkhttpclient.WithContextualMiddleware(ctx, httpclientprovider.DeleteHeadersMiddleware(list.Items...))
+		for _, k := range list.Items {
+			h.DeleteHTTPHeader(k)
+		}
 	}
-
-	return ctx
 }
 
 func (m *ClearAuthHeadersMiddleware) QueryData(ctx context.Context, req *backend.QueryDataRequest) (*backend.QueryDataResponse, error) {
@@ -45,7 +43,7 @@ func (m *ClearAuthHeadersMiddleware) QueryData(ctx context.Context, req *backend
 		return m.next.QueryData(ctx, req)
 	}
 
-	ctx = m.clearHeaders(ctx, req.PluginContext, req)
+	m.clearHeaders(ctx, req)
 
 	return m.next.QueryData(ctx, req)
 }
@@ -55,7 +53,7 @@ func (m *ClearAuthHeadersMiddleware) CallResource(ctx context.Context, req *back
 		return m.next.CallResource(ctx, req, sender)
 	}
 
-	ctx = m.clearHeaders(ctx, req.PluginContext, req)
+	m.clearHeaders(ctx, req)
 
 	return m.next.CallResource(ctx, req, sender)
 }
@@ -65,7 +63,7 @@ func (m *ClearAuthHeadersMiddleware) CheckHealth(ctx context.Context, req *backe
 		return m.next.CheckHealth(ctx, req)
 	}
 
-	ctx = m.clearHeaders(ctx, req.PluginContext, req)
+	m.clearHeaders(ctx, req)
 
 	return m.next.CheckHealth(ctx, req)
 }