Add distinct specification to QueryService

[egvimo]

This would allow to use the distinct method in the generated EntityQueryService.

So this

Specification<ENTITY> specification = Specification.where(null);

would result in this

Specification<ENTITY> specification = Specification.where(distinct(false));

So the queries would stay the same but it could be changed to a distinct query.

With a little tweaking this boolean Flag could be provided via Criteria class, so it could be queried from the API.

[CLAassistant]

All committers have signed the CLA.

[egvimo]

Are the tests failing because of my change? Locally I can compile this.

[DanielFran]

@egvimo Can you rebase with main? We had some issues last weeks and now it seems ok...

[egvimo]

@DanielFran Done. Now the workflows are waiting for approval.

[DanielFran]

Thanks @egvimo for the contribution