code: public List<String> getAllColumnsToProject() {
      return ImmutableList.<String> builder().addAll(getKeyColumnsToProject()).addAll(getDeltaColumnsToProject()).build();
    }
docs: Combine both key columns and delta columns to project
  {@inheritDoc}
  @see org.apache.gobblin.audit.values.policy.column.ColumnProjectionPolicy#getAllColumnsToProject()