TUN-6775: Add middleware.Handler verification to ProxyHTTP

ProxyHTTP now processes middleware Handler before executing the request.
A chain of handlers is now executed and appropriate response status
codes are sent.

ingress/middleware/middleware.go

@@ -5,6 +5,15 @@ import (
 	"net/http"
 )
 
-type Handler interface {
-	Handle(ctx context.Context, r *http.Request) error
+type HandleResult struct {
+	// Tells that the request didn't passed the handler and should be filtered
+	ShouldFilterRequest bool
+	// The status code to return in case ShouldFilterRequest is true.
+	StatusCode int
+	Reason     string
+}
+
+type Handler interface {
+	Name() string
+	Handle(ctx context.Context, r *http.Request) (result *HandleResult, err error)
 }