Deferred columns inconsistency

We are using deferred column:

```
d_column = column_property(
func.pg_func(id), deferred=True)
```

It gave a naming error -- as SQL Alchemy generated column name on that. Hence we label it:

```
d_column = column_property(
func.pg_func(id).label('test'), deferred=True)
```

All works fine since that point, but this column doesn't appear in a sort.
Questions:
* Should it appear?
* If not -- why its name is validated?

Start by reproducing the deferred column_property example with SQLAlchemy and inspect the repository's sorting and column-name validation entry points; no file or test is named in the issue. Compare labeled and unlabeled deferred columns, then establish and test the intended behavior for sorting and validation.

Escrita pelo modelo de indexação a partir do texto da issue.