[5.1] Fix wrong PDO bindings when using whereHas()

[marcotisi]

Hi guys,

this PR will fix a bug with Eloquent Builder when querying a scoped Model using whereHas().
I create a test which fully explain the situation.

Basically when merging wheres to the $hasQuery, the bindings should not be the complete query bindings (which includes join also) but only where bindings.

I think that this should resolve #11261, #9696, #9628

Before:

$hasQuery->mergeWheres(
    $relationQuery->wheres, $relationQuery->getBindings()
);

After:

$whereBindings = array_get($relationQuery->getRawBindings(), 'where', []);
$hasQuery->mergeWheres($relationQuery->wheres, $whereBindings);

[taylorotwell]

@acasar is this correct?

[acasar]

@taylorotwell Looks good 👍

I was thinking we could add an optional $type parameter to getBindings() so we could do:

$relationQuery->getBindings('where')

instead of:

array_get($relationQuery->getRawBindings(), 'where', [])

But this might be a breaking change?

Also, this won't merge into 5.3 easily. It may be easier to just transfer the code manually.

[marcotisi]

I think that this bug is also present in branches 5.2 and 5.3, but unfortunately debugging this was a big deal, and I think I don't have the time to do also for 5.2 and 5.3 branches.

[taylorotwell]

@acasar would it be hard to send a PR for this to the 5.3 branch?

[acasar]

@taylorotwell Shouldn't be that hard. I'll prepare a PR later today.