[Feature] Flexibility joinRelationship with Initial Model. For some case Support MorphTo joins Nested.

[illusi03]

Dear Maintainers,

I hope this message finds you well. I am very excited and interested in enhancing the functionality of this package. I have been following the development of Eloquent Power Joins, and I am truly impressed by its ability to simplify and optimize complex database queries in Laravel.

Unfortunately, I am facing a problem where I can't perform a nested join in a MorphTo relationship.

For error nested example :

->joinRelationship(
    'medicalRecordable.creator',
    morphable: Customer::class,
)

The above code doesn't work. I understand that the morphable parameter can cause confusion when dealing with nested relationships. Therefore, I took the initiative to improve the joinRelationship() function to make it more flexible.

Improved example :

->joinRelationship(
    'medicalRecordable',
    morphable: Customer::class,
)
->joinRelationship(
    'creator',
    initialModel: User::class,
)

The above code works seamlessly. I would like to create a Pull Request based on this issue.
I am open to discussion if anyone has a better solution.
Thanks a lot.

[luisdalmolin]

Hmm, I do understand your issue, but I'm not sure I'm a big fan of yet another parameter without a lot of meaning. Wouldn't this be the case where morphable needs to work in nested relationships?

Something like:

->joinRelationship(
    'medicalRecordable.creator',
    ['creator' => fn ($join) => $join->morphable(Customer::class),
)