expose fewer internals in packages, for easier software reuse

- prometheus is now behind an interface, they aren't dependencies for the
  reusable components anymore.
- some dependencies have been inverted: instead of packages importing a main
  package to get configuration, the main package now sets configuration in
  these packages. that means fewer internals are pulled in.
- some functions now have new parameters for values that were retrieved from
  package "mox-".

metrics/http.go

@@ -1,65 +0,0 @@
-// Package metrics has prometheus metric variables/functions.
-package metrics
-
-import (
-	"context"
-	"errors"
-	"fmt"
-	"os"
-	"time"
-
-	"golang.org/x/exp/slog"
-
-	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/client_golang/prometheus/promauto"
-
-	"github.com/mjl-/mox/mlog"
-)
-
-var (
-	metricHTTPClient = promauto.NewHistogramVec(
-		prometheus.HistogramOpts{
-			Name:    "mox_httpclient_request_duration_seconds",
-			Help:    "HTTP requests lookups.",
-			Buckets: []float64{0.01, 0.05, 0.100, 0.5, 1, 5, 10, 20, 30},
-		},
-		[]string{
-			"pkg",
-			"method",
-			"code",
-			"result",
-		},
-	)
-)
-
-// HTTPClientObserve tracks the result of an HTTP transaction in a metric, and
-// logs the result.
-func HTTPClientObserve(ctx context.Context, log mlog.Log, pkg, method string, statusCode int, err error, start time.Time) {
-	log = log.WithPkg("metrics")
-	var result string
-	switch {
-	case err == nil:
-		switch statusCode / 100 {
-		case 2:
-			result = "ok"
-		case 4:
-			result = "usererror"
-		case 5:
-			result = "servererror"
-		default:
-			result = "other"
-		}
-	case errors.Is(err, os.ErrDeadlineExceeded) || errors.Is(err, context.DeadlineExceeded):
-		result = "timeout"
-	case errors.Is(err, context.Canceled):
-		result = "canceled"
-	default:
-		result = "error"
-	}
-	metricHTTPClient.WithLabelValues(pkg, method, result, fmt.Sprintf("%d", statusCode)).Observe(float64(time.Since(start)) / float64(time.Second))
-	log.Debugx("httpclient result", err,
-		slog.String("pkg", pkg),
-		slog.String("method", method),
-		slog.Int("code", statusCode),
-		slog.Duration("duration", time.Since(start)))
-}