implement grpc gateway and addl handler support

pkg/srv/http/http.go

@@ -57,6 +57,15 @@ func prepHTTPServer(opts *opts.AppHTTP) *http.Server {
 			Msg("mounted prometheus metrics endpoint")
 	}
 
+	// Inject extra handlers if given
+	// Used for grpc-gateway runtime.ServeMux handlers
+	for _, h := range opts.Handlers {
+		if h.StripPrefix {
+			h.Handler = http.StripPrefix(h.Prefix, h.Handler)
+		}
+		mux.Handle(h.Prefix, h.Handler)
+	}
+
 	// Add OTEL, skip health-check spans
 	// NOTE: Add any other span exclusions here
 	handler := otelhttp.NewHandler(mux, "/",