Adding stream group creation

Summary:
Uploader stream group wraps a dgw stream group and provides a single point for all communication.

The group will be created once auth creds are available and will be recreated on any error.

Differential Revision: D64174403

fbshipit-source-id: 9ac9c1a31290284977d9f89aa066af398aa16128

proxygen/httpserver/Mocks.h

@@ -10,6 +10,7 @@
 
 #include <folly/portability/GMock.h>
 #include <proxygen/httpserver/RequestHandler.h>
+#include <proxygen/httpserver/RequestHandlerFactory.h>
 #include <proxygen/httpserver/ResponseHandler.h>
 
 namespace proxygen {
@@ -104,4 +105,15 @@ class MockRequestHandler : public RequestHandler {
   }
 };
 
+class MockRequestHandlerFactory : public RequestHandlerFactory {
+ public:
+  ~MockRequestHandlerFactory() override = default;
+  MOCK_METHOD(void, onServerStart, (folly::EventBase*), (noexcept, override));
+  MOCK_METHOD(void, onServerStop, (), (noexcept, override));
+  MOCK_METHOD((RequestHandler*),
+              onRequest,
+              (RequestHandler*, HTTPMessage*),
+              (noexcept, override));
+};
+
 } // namespace proxygen