Pull request 2275: AGDNS-2374-slog-stats

Squashed commit of the following:

commit 45b2fc6a05a4f7775d2b6fa056c81d53d4f402d7
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Thu Sep 5 18:07:06 2024 +0300

    all: imp code

commit 022c90496a46b0a0423dd2cb1c02a3473ba5d224
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Wed Sep 4 19:32:35 2024 +0300

    stats: imp code

commit bb3c0c8002c34bec7440cd93b7833f7022eef0d8
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Wed Sep 4 19:10:36 2024 +0300

    all: imp code

commit 363a16f6bb2faa1d9b890b4967684129208af62e
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Wed Sep 4 17:45:31 2024 +0300

    all: imp code

commit a3c96e3d211cc5e11ba09e334748f65a44b8960a
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Mon Sep 2 20:44:11 2024 +0300

    stats: imp code

commit 2c0ffd91fddd286254b53be790146a2931b7b55b
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Mon Sep 2 19:47:11 2024 +0300

    all: slog stats

internal/aghhttp/aghhttp.go

@@ -2,13 +2,16 @@
 package aghhttp
 
 import (
+	"context"
 	"fmt"
 	"io"
+	"log/slog"
 	"net/http"
 
 	"github.com/AdguardTeam/AdGuardHome/internal/version"
 	"github.com/AdguardTeam/golibs/httphdr"
 	"github.com/AdguardTeam/golibs/log"
+	"github.com/AdguardTeam/golibs/logutil/slogutil"
 )
 
 // HTTP scheme constants.
@@ -31,12 +34,39 @@ func OK(w http.ResponseWriter) {
 }
 
 // Error writes formatted message to w and also logs it.
+//
+// TODO(s.chzhen):  Remove it.
 func Error(r *http.Request, w http.ResponseWriter, code int, format string, args ...any) {
 	text := fmt.Sprintf(format, args...)
 	log.Error("%s %s %s: %s", r.Method, r.Host, r.URL, text)
 	http.Error(w, text, code)
 }
 
+// ErrorAndLog writes formatted message to w and also logs it with the specified
+// logging level.
+func ErrorAndLog(
+	ctx context.Context,
+	l *slog.Logger,
+	r *http.Request,
+	w http.ResponseWriter,
+	code int,
+	format string,
+	args ...any,
+) {
+	text := fmt.Sprintf(format, args...)
+	l.ErrorContext(
+		ctx,
+		"http error",
+		"host", r.Host,
+		"method", r.Method,
+		"raddr", r.RemoteAddr,
+		"request_uri", r.RequestURI,
+		slogutil.KeyError, text,
+	)
+
+	http.Error(w, text, code)
+}
+
 // UserAgent returns the ID of the service as a User-Agent string.  It can also
 // be used as the value of the Server HTTP header.
 func UserAgent() (ua string) {