Consistent behaviour between MessageBag constructor and public API

[michaeldyrynda]

Currently, the behaviour between initialising a new MessageBag and using the add method is inconsistent.

The add method tests for uniqueness (of the key, and the message in the keyed array), whereas the constructor will accept duplicate messages.

$messageBag = new MessageBag(['messages' => ['first', 'second', 'third', 'third']]);

// $messageBag->getMessages()
// ['messages' => ['first', 'second', 'third', 'third']]

$messageBag = new MessageBag;
$messageBag->add('messages', 'first');
$messageBag->add('messages', 'second');
$messageBag->add('messages', 'third');
$messageBag->add('messages', 'third');

// $messageBag->getMessages()
// ['messages' => ['first', 'second', 'third']

I'm not certain if this is on purpose, so I propose to fix the constructor behaviour, which will bring consistency between the constructor and public API of the MessageBag (add) method.

It appears this has been around since January, 2013, so this would likely be targeted to next release due to backwards compatibility breakage.

[taylorotwell]

Yeah we should fix this.

[sahilsharma011]

@taylorotwell If no one is working on this, then I would like to get assigned on this issue.

[taylorotwell]

If this isn't fixed yet, I'm open to PRs.