[GIN] Log filter rule matching

internal/db/db_gin.go

@@ -220,6 +220,7 @@ func isAddressAllowed(email string) bool {
 			log.Error(2, "Invalid pattern: %v", err)
 		}
 		if match {
+			log.Trace("New user email %q matched filter rule %q (Allow: %t)", email, line, allow)
 			return allow
 		}
 	}