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/github.com/prometheus/common/model/metadata.go

@@ -0,0 +1,28 @@
+// Copyright 2023 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package model
+
+// MetricType represents metric type values.
+type MetricType string
+
+const (
+	MetricTypeCounter        = MetricType("counter")
+	MetricTypeGauge          = MetricType("gauge")
+	MetricTypeHistogram      = MetricType("histogram")
+	MetricTypeGaugeHistogram = MetricType("gaugehistogram")
+	MetricTypeSummary        = MetricType("summary")
+	MetricTypeInfo           = MetricType("info")
+	MetricTypeStateset       = MetricType("stateset")
+	MetricTypeUnknown        = MetricType("unknown")
+)