Test fetch ID only

[nPraml]

Hello @rbygrave ,

I wrote the tests for issue #3643.
In all three cases, I would expect the same SQL query to be output: select t0.id, t0.status, t0.kcustomer_id from o_order t0

[rPraml]

We might have found a solution for this: After the fetchpaths are sorted, and missing paths are added, we check the result and try to remove/convert id-only fetches in a select of the parent path

[nPraml]

Hi @rbygrave ,

We prefer this solution over #3646.
We've adopted this in our fork and successfully tested it in our application.
Could you please take a look?