fix: allow configuring excess versions alerting (#19028)

Bonus: enable audit alerts for object versions
beyond the configured value, default is '100'
versions per object beyond which scanner will
alert for each such objects.

cmd/object-handlers.go

@@ -2360,9 +2360,18 @@ func (api objectAPIHandlers) PutObjectHandler(w http.ResponseWriter, r *http.Req
 		Host:         handlers.GetSourceIP(r),
 	}
 	sendEvent(evt)
-	if objInfo.NumVersions > dataScannerExcessiveVersionsThreshold {
+	if objInfo.NumVersions > int(scannerExcessObjectVersions.Load()) {
 		evt.EventName = event.ObjectManyVersions
 		sendEvent(evt)
+
+		auditLogInternal(context.Background(), AuditLogOptions{
+			Event:     "scanner:manyversions",
+			APIName:   "PutObject",
+			Bucket:    objInfo.Bucket,
+			Object:    objInfo.Name,
+			VersionID: objInfo.VersionID,
+			Status:    http.StatusText(http.StatusOK),
+		})
 	}
 
 	// Do not send checksums in events to avoid leaks.