[5.4] Set connection while retrieving models

[themsaid]

In #17395 we moved the model's create() and forceCreate() methods to the Builder to allow something like User::on('myCustomConnection')->create();, before that creating a model on a different collection was a bit hacky.

After that it was pretty obvious that hydrate() and fromQuery() can be moved to the builder instance as well, since we won't have to pass that $connection argument and we just get it from the Builder instance, that's when 1ae29d9 was committed.

However in that commit we removed the argument but forgot to pass the connection name from the Builder instance, leaving the connection as null when we retrieve a model.

In this PR we simply set the connection using $this->query->getConnection()->getName(), just like we do in create() and forceCreate().

This will solve the failing test in #18760 without having to re-introduce the $connection argument to the hydrate() method.

[adamwathan]

Perfect, thanks @themsaid!

[adamwathan]

Looks like there's a good opportunity to extract this to a method:

$instance = $this->model->newInstance($attributes)->setConnection(
    $this->query->getConnection()->getName()
);

Appears 7 times! 😄

[taylorotwell]

@themsaid if you see a good way to extract that method go for it 😄

[themsaid]

@adamwathan yeah looks like a great candidate for having an own method, will PR that in a while :)