Trait HasRelationships::addRelation should accept a forth parameter to override existent relation

[goldmont]

Hi,

The current behaviour of HasRelationships::addRelation is to fail when the developer tries to override an existing relation via the add*Relation() methods. This is due to this line. I expect to have the ability to override an existing relation because currently I have to use the PHP native way.

Example
\Backend\Models\User model:
I would like to override the value of the avatar relation in order to use my custom File::class implementation.

public $attachOne = [
    'avatar' => \System\Models\File::class
];

The following approach doesn't work:

\Backend\Models\User::extend(function ($model) {
	$model->addAttachOneRelation('avatar', [
		File::class
	]);
});

It fails with the following error:

Cannot add the "avatar" relation to Backend\Models\User, it conflicts with an existing relation, attribute, or property. in /var/www/vendor/winter/storm/src/Database/Concerns/HasRelationships.php:817

As a workaround, I can do this:

\Backend\Models\User::extend(function ($model) {
	$model->attachOne['avatar'] = [
		File::class
	];
});

---

It would be nice to do something like this:

\Backend\Models\User::extend(function ($model) {
	$model->addAttachOneRelation('avatar', [
		File::class
	], override: true);
});

What do you think about it? Thank you.

[mjauvin]

Please submit a PR, I also think this is a welcome improvement.

[goldmont]

Sure. override is good to you as parameter name?

[mjauvin]

Yes, if not the other maintainers will suggest an alternative.

[goldmont]

I'll wait till tomorrow.

[mjauvin]

No need, go ahead with the PR and that can be suggested there