[10.x] Fixed incorrect assumption in QueriesRelationships that the owner key is necessarily the model key

[GrahamCampbell]

Fixes a bug introduced earlier (#38668) that nobody noticed because:

1. Using a whereMorphedTo is a pretty rare use case. I've never used it before, and neither does any of the first party library code that I have locally.
2. Almost all of the time the owner id will be the same as the related model id, as that's the default and it's unusual to change it.

[GrahamCampbell]

cc @tobyzerner

[GrahamCampbell]

Ok, I'm not sure why the tests are failing here. getRelatedKeyFrom just runs $model->{$this->ownerKey} which is the same as what we had before in $model->getKey() whenever the key column and owner column are the same, and they both are set to id in the tests?

[tobyzerner]

Good catch @GrahamCampbell! Not sure why the tests are failing either, strange 🤔

[staudenmeir]

getRelatedKeyFrom() is a protected method and so the call is handled by Relation::__call() which throws a BadMethodCallException exception (that somehow doesn't show up).

[GrahamCampbell]

Thanks. My 10:30PM brain didn't even think to check that the method was not public. 😆

[taylorotwell]

Probably need a test for this.

[driesvints]

@GrahamCampbell feel free to resend this with a test, thanks.