p2.7: prometheus /metrics

Default GET /metrics is Prometheus text; JSON stays at /metrics.json
and ?format=json. :8443 needs the metrics caller bearer; loopback
stays open. Restricted callers have no per-caller series and no
tavily:restricted gauge.

vendor/google.golang.org/protobuf/proto/proto_methods.go

@@ -0,0 +1,20 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// The protoreflect build tag disables use of fast-path methods.
+//go:build !protoreflect
+// +build !protoreflect
+
+package proto
+
+import (
+	"google.golang.org/protobuf/reflect/protoreflect"
+	"google.golang.org/protobuf/runtime/protoiface"
+)
+
+const hasProtoMethods = true
+
+func protoMethods(m protoreflect.Message) *protoiface.Methods {
+	return m.ProtoMethods()
+}