Hybrid support for BelongsToMany relationship

[hans-thomas]

Hi, I noticed the lines that we removed in #2664 (comment) PR, were part of handling the hybrid relationship that was not covered by tests.
This PR is continuing #2276. Thanks to @juniohyago.

• Updating eloquent model instance with latest relation data

[hans-thomas]

The relation data of the current eloquent model instance doesn't update. It has to be fixed to prevent users from fetching the latest relationship data from DB each time or it's possible to make users confused.

[GromNaN]

Do we really want to have a pivot table here? If the relations are already stored in the MongoDB document, it should not be duplicated in an SQL table.

[hans-thomas]

laravel-mongodb/src/Eloquent/HybridRelations.php

Lines 290 to 301 in fc1f9cc

	// Check if it is a relation with an original model.
	if (! is_subclass_of($related, MongoDBModel::class)) {
	return parent::belongsToMany(
	$related,
	$collection,
	$foreignPivotKey,
	$relatedPivotKey,
	$parentKey,
	$relatedKey,
	$relation,
	);
	}

The sql models don't reach our BelongsToMany class. So, we can't control this behavior.
As I know, the sql models, store their relations data in a pivot tabel and mongo models, store theirs in a pivot column.

[hans-thomas]

Hi @GromNaN, Could you please merge these two PRs?
I know you're super busy but I will be gone from next week for at least 2 months (it can be increased to one and a half years) and I don't have access to the Internet in that period.
Is there any chance to release the v4.1?

[GromNaN]

It seems feasible today.

[hans-thomas]

It would be awesome😁🔥
before releasing it, I want to open one more PR for BelongsToMany relation. I noticed some potential bugs when we set custom keys.

[GromNaN]

Thank you @hans-thomas. I'm merging the other one and wait for your new PR.