feat(logging): date time layout (#6333)

This adds a date time layout option for the log file path.

Closes #6136

docs/content/en/configuration/miscellaneous/logging.md

@@ -78,9 +78,11 @@ Logs can be stored in a file when file path is provided. Otherwise logs are writ
 level to `debug` or `trace` this will generate large amount of log entries. Administrators will need to ensure that
 they rotate and/or truncate the logs over time to prevent significant long-term disk usage.
 
-If you include the value `%d` in the filename it will replace this value with a date time indicative of the time
-the logger was initialized using [RFC3339](https://datatracker.ietf.org/doc/html/rfc3339) as the format which is
-represented as `2006-01-02T15:04:05Z07:00` in go.
+There are two replacements that exist in this string for the purpose of including the dete. The `%d` value which just
+uses the [RFC3339] layout, and the `{datetime}` replacement which by
+default uses the [RFC3339] layout, but optionally can be suffixed with the
+[Go Layout](https://pkg.go.dev/time#pkg-constants) semantics in the format of `{datetime:<layout>}` where `<layout>` is
+the layout supported by Go.
 
 #### File Path Examples
 
@@ -98,6 +100,13 @@ log:
   file_path: /config/authelia.%d.log
 ```
 
+__Date Time Example (with custom layout):__
+
+```yaml
+log:
+  file_path: /config/authelia.{datetime:Mon Jan 2 15:04:05 MST 2006}.log
+```
+
 ### keep_stdout
 
 {{< confkey type="boolean" default="false" required="no" >}}

internal/logging/logger.go

@@ -3,6 +3,7 @@ package logging
 import (
 	"io"
 	"os"
+	"regexp"
 	"strings"
 	"time"
 
@@ -44,6 +45,24 @@ func InitializeLogger(config schema.Log, log bool) (err error) {
 	return ConfigureLogger(config, log)
 }
 
+var reFormatFilePath = regexp.MustCompile(`(%d|\{datetime(:([^}]+))?})`)
+
+func FormatFilePath(in string, now time.Time) (out string) {
+	matches := reFormatFilePath.FindStringSubmatch(in)
+
+	if len(matches) == 0 {
+		return in
+	}
+
+	layout := time.RFC3339
+
+	if len(matches[3]) != 0 {
+		layout = matches[3]
+	}
+
+	return strings.Replace(in, matches[0], now.Format(layout), 1)
+}
+
 // ConfigureLogger configures the default loggers level, formatting, and the output destinations.
 func ConfigureLogger(config schema.Log, log bool) (err error) {
 	setLevelStr(config.Level, log)
@@ -61,7 +80,7 @@ func ConfigureLogger(config schema.Log, log bool) (err error) {
 	case config.FilePath != "":
 		var file *os.File
 
-		if file, err = os.OpenFile(strings.ReplaceAll(config.FilePath, "%d", time.Now().Format(time.RFC3339)), os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0600); err != nil {
+		if file, err = os.OpenFile(FormatFilePath(config.FilePath, time.Now()), os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0600); err != nil {
 			return err
 		}
 

internal/logging/logger_test.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"runtime"
 	"testing"
+	"time"
 
 	"github.com/sirupsen/logrus"
 	"github.com/stretchr/testify/assert"
@@ -14,6 +15,46 @@ import (
 	"github.com/authelia/authelia/v4/internal/configuration/schema"
 )
 
+func TestFormatFilePath(t *testing.T) {
+	testCases := []struct {
+		name     string
+		have     string
+		now      time.Time
+		expected string
+	}{
+		{
+			"ShouldReturnInput",
+			"abc 123",
+			time.Unix(0, 0).UTC(),
+			"abc 123",
+		},
+		{
+			"ShouldReturnStandardWithDateTime",
+			"abc %d 123",
+			time.Unix(0, 0).UTC(),
+			"abc 1970-01-01T00:00:00Z 123",
+		},
+		{
+			"ShouldReturnStandardWithDateTimeFormatter",
+			"abc {datetime} 123",
+			time.Unix(0, 0).UTC(),
+			"abc 1970-01-01T00:00:00Z 123",
+		},
+		{
+			"ShouldReturnStandardWithDateTimeCustomLayout",
+			"abc {datetime:Mon Jan 2 15:04:05 MST 2006} 123",
+			time.Unix(0, 0).UTC(),
+			"abc Thu Jan 1 00:00:00 UTC 1970 123",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			assert.Equal(t, tc.expected, FormatFilePath(tc.have, tc.now))
+		})
+	}
+}
+
 func TestShouldWriteLogsToFile(t *testing.T) {
 	dir := t.TempDir()