Fix #175 : embedsMany duplicates are identified by key

[alexandre-butynski]

The exists attribute is not enough reliable to detect duplicates in embedsMany documents. I just wrote a small contains() method that is used instead.

[jenssegers]

Can you show me the code example when it would fail without the contains?

[alexandre-butynski]

I wrote a failing test case before writing the code. The simple example below save two records with the same _id in the _addresses attribute :

$addressData = array('_id' => new MongoId);
$user->adresses()->create($addressData);
$user->adresses()->create($addressData);

This happens when data come from a form, for example when you update the existing addresses of a user.

[jenssegers]

Why would you create objects like that?

[alexandre-butynski]

I don't want to create objects, I want to save data in my database. These data come from a form filled by the user.

Something like that :

$user->adresses()->createMany(Input::get('addresses');

When the user want to update its addresses, a hidden field with the existing _id is sent with the text fields values in order to not erase and resave all the embedded items (of course, my use case is more complex than basic adresses).

[jenssegers]

I'm going to merge this, it kind of makes sense to check primary keys.