[feature] Initial Prometheus metrics implementation (#2334)

* feat: Initial OTEL metrics

* docs: add metrics documentation

* fix: metrics endpoint conditional check

* feat: metrics endpoint basic auth

* fix: make metrics-auth-enabled default false

* fix: go fmt helpers.gen.go

* fix: add metric-related env vars to envparsing.sh

* fix: metrics docs

* fix: metrics related stuff in envparsing.sh

* fix: metrics docs

* chore: metrics docs wording

* fix: metrics stuff in envparsing?

* bump otel versions

---------

Co-authored-by: Tsuribori <user@acertaindebian>
Co-authored-by: Tsuribori <none@example.org>
Co-authored-by: tsmethurst <tobi.smethurst@protonmail.com>

vendor/github.com/technologize/otel-go-contrib/otelginmetrics/config.go

@@ -0,0 +1,45 @@
+package otelginmetrics
+
+import (
+	"net/http"
+
+	"go.opentelemetry.io/otel/attribute"
+	semconv "go.opentelemetry.io/otel/semconv/v1.7.0"
+)
+
+type config struct {
+	recordInFlight bool
+	recordSize     bool
+	recordDuration bool
+	groupedStatus  bool
+	recorder       Recorder
+	attributes     func(serverName, route string, request *http.Request) []attribute.KeyValue
+	shouldRecord   func(serverName, route string, request *http.Request) bool
+}
+
+func defaultConfig() *config {
+	return &config{
+		recordInFlight: true,
+		recordDuration: true,
+		recordSize:     true,
+		groupedStatus:  true,
+		attributes:     DefaultAttributes,
+		shouldRecord: func(_, _ string, _ *http.Request) bool {
+			return true
+		},
+	}
+}
+
+var DefaultAttributes = func(serverName, route string, request *http.Request) []attribute.KeyValue {
+	attrs := []attribute.KeyValue{
+		semconv.HTTPMethodKey.String(request.Method),
+	}
+
+	if serverName != "" {
+		attrs = append(attrs, semconv.HTTPServerNameKey.String(serverName))
+	}
+	if route != "" {
+		attrs = append(attrs, semconv.HTTPRouteKey.String(route))
+	}
+	return attrs
+}