[12.x] fix: add TPivotModel default and define pivot property in {Belongs,Morph}ToMany

[calebdw]

Hello!

This cleans up the TPivotModel implementation in #55053 to use a default so users don't need to set the template if not needed. It also uses the template to define the pivot property on the resultant records.

Note that there is currently a PHPStan bug that prevents the TAccessor template from being used as an object key. As soon as that bug is fixed I will submit another PR.

Closes larastan/larastan#1774, closes #55078
CC: @browner12 , @AJenbo

Thanks!

[crynobone]

There are use cases where project using \Illuminate\Database\Eloquent\Relations\Concerns\AsPivot&\Illuminate\Database\Eloquent\Model instead of \Illuminate\Database\Eloquent\Relations\Pivot

[crynobone]

e.g: laravel/nova-issues#6671

[AJenbo]

It might be necessary to have an interface for this

[calebdw]

\Illuminate\Database\Eloquent\Relations\Concerns\AsPivot&\Illuminate\Database\Eloquent\Model is not a correct type because you can't have a trait in a intersection type:

• https://phpstan.org/r/72b3d4d3-eb17-4004-823b-f2724d2c7f76

The user just needs to extend from Pivot/MorphPivot

[taylorotwell]

@calebdw does this have any negative affect on PHP Storm and VS Code experience?

[calebdw]

Not that I know of, this should improve the experience as the code now better understands that the pivot property exists

[calebdw]

Thank you sir!