Make fields conditionable

[gizburdt]

Would be awesome if a field is conditionable, so we can make it filterable based on a condition. Like so:

BelongsTo::make('Site')
    ->when(1 == 1, function ($field) {
        $field->filterable();
    }),

[crynobone]

At the moment you can do the following:

BelongsTo::make('Site')
    ->tap(function ($field) {
        if (1 == 1) {
            $field->filterable();
        }
    }),