JSON encoding / decoding customization for JSON based cass

[taylorotwell]

This PR allows the customization of json_encode and json_decode for the array and collection casts, as well as AsArrayObject, AsCollection, AsEnumArrayObject, etc.

use Illuminate\Database\Eloquent\Casts\Json;

Json::encodeUsing(fn ($value) => json_encode($value));

Json::decodeUsing(fn ($value, $associative) => json_decode($value, $associative));

This customization would typically be done in a service provider.

[driesvints]

@taylorotwell I guess these need to become static?

[morloderex]

What if 2 columns within the same project needs different json encoding / decoding? This customization object seems to be global? Would that require a custom cast?

[taylorotwell]

@morloderex I guess that require a custom cast. My thinking was that if you're using something like JSON_UNESCAPED_UNICODE you probably want that on all your JSON casts throughout your application.