code: public GenerationType convertToEnum() {
      if (GenerationType.IDENTITY.name().equalsIgnoreCase(value)) {
        return GenerationType.IDENTITY;
      }
      if (GenerationType.SEQUENCE.name().equalsIgnoreCase(value)) {
        return GenerationType.SEQUENCE;
      }
      if (GenerationType.TABLE.name().equalsIgnoreCase(value)) {
        return GenerationType.TABLE;
      }
      return null;
    }
docs: {@link GenerationType} に変換します。
  
  @return 対応する {@link GenerationType}