[Fix] Static analysis of DataCollection::map(...) and DataCollection::through(...) methods

[joelbutcher]

The problem

The static analysis type hinting for DataCollection::map(...) and DataCollection::through(...) expect the return type of the passed closures to match the same type of each item within the collection. Typically the map method of arrays, or Laravel collections, is used to transform a collection of items into something different (i.e. a different collection of items, who's types may not match the initial collections types).

Currently, this expectation can lead to static analysis errors such as:

Parameter #1 $map of method Spatie\LaravelData\DataCollection<int, App\Data\Foo>::map() expects callable(App\Data\Foo, int): App\Data\Foo, Closure(App\Data\Foo, int): App\Data\Bar given

The fix

The fix here is is to add another template to both these methods TMapValue to use as the return type, which may or may not be the same type as items in the collection

[rubenvanassche]

Thanks!