feat: Access Logging on the user server

Closes: #98

Co-authored-by: Roberto Abdelkader Martínez Pérez <robertomartinezp@gmail.com>

internal/logger/logger.go

@@ -1,12 +1,45 @@
 package logger
 
 import (
+	"fmt"
 	"log"
 	"os"
+	"time"
 )
 
+var A *log.Logger
 var L *log.Logger
 
 func init() {
+	A = log.New(os.Stdout, "", 0)
 	L = log.New(os.Stderr, "", log.LstdFlags|log.Lmicroseconds|log.LUTC)
 }
+
+// See https://en.wikipedia.org/wiki/Common_Log_Format
+// Tested with love against CLFParser https://pypi.org/project/clfparser/
+func LogAccess(clientAddr, handlerId, user, method, resource, version string, status int, bytesSent int64, referer, userAgent string) {
+	clientAddr = dashIfEmpty(clientAddr)
+	handlerId = dashIfEmpty(handlerId)
+	user = dashIfEmpty(user)
+	referer = dashIfEmpty(referer)
+	userAgent = dashIfEmpty(userAgent)
+	firstLine := fmt.Sprintf("%s %s %s", method, resource, version)
+	ts := time.Now().UTC().Format("02/Jan/2006:15:04:05 -0700") // Amazing date format layout!  Not.
+	A.Printf("%s %s %s [%s] %q %d %d %q %q\n",
+		clientAddr,
+		handlerId,
+		user,
+		ts,
+		firstLine,
+		status,
+		bytesSent,
+		referer,
+		userAgent)
+}
+
+func dashIfEmpty(value string) string {
+	if value == "" {
+		return "-"
+	}
+	return value
+}