whereBelongsTo must support related model ID

[MohammadZarifiyan]

Hello, I think Laravel must add support for finding models via their related model ID:

$authorId = 123;
$authorPosts = Post::whereBelongsTo($authorId, 'author')->get();

The above code is the shorter & cleaner version of the following code:

$authorId = 123;
$authorPosts = Post::where('author_id', $authorId)->get();