public PrimaryKeySpec build() {
      if (!pkFields.isEmpty()) {
        return new PrimaryKeySpec(schema, pkFields);
      } else {
        return PrimaryKeySpec.noPrimaryKey();
      }
    }
parse primary key spec from table properties

@param schema - base store table schema
@param keyDescription - key description of {#{@link #description}}
@return primary key spec.
amoro-format-iceberg/src/main/java/org/apache/amoro/table/PrimaryKeySpec.java