[api] Fix usage of scmsync projects via project links

[adrianschroeter]

It is not enough to check only the project itself for scmsync

Fixes: #18205

[smithfarm]

@adrianschroeter This had to be reverted because nothing in the UI/API is prepared for @Package being nil in this situation.

[fwag]

hi @hennevogel @eduardoj could you kindly extend this PR so that is properly managed by UI/API?

[fwag]

Discussed with @danidoni, this pull request #18372 from @hellcp fixes this issue

[adrianschroeter]

No, it does not fix that the wrong package/project object is used for verification and the operation is run against a different project.

[danidoni]

No, it does not fix that the wrong package/project object is used for verification and the operation is run against a different project.

Okay, that's true, it only fixes part of the use cases, not all of them.

[adrianschroeter]

@danidoni but you aware that this is currently a new regression, blocking people?

Shall I resubmit this?

(Btw, it is wrong that nothing is prepared that @Package can be nil as this is the current design of the api. You have the very same thing also with packages from remote projects where you also need to be able to operate on the binaries.)

[danidoni]

Shall I resubmit this?

Sure