MM-22784 Advanced logging config for audit (#15076)

Adds the advanced logging config for audit. Existing support for auditing to a single file remains for E0 and E10 licenses instances, and a new config item ExperimentalAuditSettings.AdvancedLoggingConfig is added that behaves like LogSettings.AdvancedLoggingConfig.

Supported destinations:

- file
- syslog (with out without TLS)
- raw TCP socket (with out without TLS)

ExperimentalAuditSettings.AdvancedLoggingConfig can contain a filespec to a config file, a database DSN, or JSON.

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>
Co-authored-by: Claudio Costa <cstcld91@gmail.com>

mlog/logr.go

@@ -39,30 +39,35 @@ type LogTargetCfg map[string]*LogTarget
 type LogrCleanup func() error
 
 func newLogr(targets LogTargetCfg) (*logr.Logger, error) {
-	var errs error
-
-	lgr := logr.Logr{}
-
+	lgr := &logr.Logr{}
 	lgr.OnExit = func(int) {}
 	lgr.OnPanic = func(interface{}) {}
-
 	lgr.OnLoggerError = onLoggerError
 	lgr.OnQueueFull = onQueueFull
 	lgr.OnTargetQueueFull = onTargetQueueFull
 
+	err := logrAddTargets(lgr, targets)
+	logger := lgr.NewLogger()
+	return &logger, err
+}
+
+func logrAddTargets(lgr *logr.Logr, targets LogTargetCfg) error {
+	var errs error
 	for name, t := range targets {
-		target, err := newLogrTarget(name, t)
+		target, err := NewLogrTarget(name, t)
 		if err != nil {
 			errs = multierror.Append(err)
 			continue
 		}
 		lgr.AddTarget(target)
 	}
-	logger := lgr.NewLogger()
-	return &logger, errs
+	return errs
 }
 
-func newLogrTarget(name string, t *LogTarget) (logr.Target, error) {
+// NewLogrTarget creates a `logr.Target` based on a target config.
+// Can be used when parsing custom config files, or when programmatically adding
+// built-in targets. Use `mlog.AddTarget` to add custom targets.
+func NewLogrTarget(name string, t *LogTarget) (logr.Target, error) {
 	formatter, err := newFormatter(name, t.Format)
 	if err != nil {
 		return nil, err