code: protected static String createUniqueSchema() {
          String uuid = UUID.randomUUID().toString();
          uuid = allowedSchemaChars.retainFrom(uuid);
          String schema = 'u' + uuid;
          return schema;
      }
docs: Creates a unique string usable as a schema name. Constructed with the
  character 'u' plus a UUID (stripped of non-alphanumeric characters).
  @return the unique string