Can firstOrNew be used with belongsToMany relationships in polymorphic scenarios

1. There is an issue where using `firstOrNew()` with `belongsToMany` relationships can return the first record in the database, even if the related record already exists[1].

2. The expected behavior is for `firstOrNew()` to return a new instance if the record doesn't exist, similar to how `first()` behaves. However, they have different behaviors in this case[1].

3. This issue appears to still be present in the latest versions of Laravel as of October 2023[1].

4. The search results do not provide a clear solution or workaround for using `firstOrNew()` with `belongsToMany` relationships in polymorphic scenarios.

In general, `firstOrNew()` is used to efficiently check if a record exists and create a new instance if it doesn't. However, when dealing with complex relationships like `belongsToMany` and polymorphic scenarios, it seems that the expected behavior is not always guaranteed.

If you encounter this issue, you may need to use alternative approaches, such as manually checking if the record exists using `first()` or `where()` before creating a new instance. Alternatively, you could use `firstOrCreate()` instead of `firstOrNew()` to create the record if it doesn't exist.

It's recommended to thoroughly test your code and be aware of the potential unexpected behavior when using `firstOrNew()` with complex relationships in Laravel.