[4.1.x] Fluent syntax FieldGroup

[tabacitu]

For when you want to apply a change/definition to multiple fields. The syntax I have in mind is something like this:

        CRUD::fieldGroup([
            CRUD::field('text'),
            CRUD::field('number')->type('number'),
            CRUD::field('email')->type('email'),
        ])
        ->tab('Simple')
        ->size(6);

The name might still need some work:

CRUD::fieldGroup([]); // singular
CRUD::fieldGroup([]); // plural maybe?!?!
CRUD::fields([]); // this already exists as a getter though

For this to happen, we need to create a new object, ex FieldGroup or FieldCollection, which would be Fluent to allow subsequent calls on it, and each call would basically forward that call to the fields inside that group, to modify their definition.

[sergeyugai]

hi @tabacitu,
here i am again with my backpack-fields package :)
I did something similar here: https://github.com/sergeyugai/backpack-fields-as-classes#field-collections - so once #2604 is resolved (or, well, when documentation is updated), I can re-generate my backpack fields and add your syntax as well.

Actually, there is one example missing from my readme:

$this->crud->addFields(


   FieldsCollection::make([
       NumericField::make('min_price_of_item', 'Min price of item'),
       NumericField::make('max_price_of_item', 'Max price of item')
   ])->prefix('$')->attributes(['step' => '5'])->tab('Pricing')->toArray()


);   

[tabacitu]

Update: there's a working PR for this from @pxpm . Anybody who stumbles upon this please check out #2951 . Especially you @sergeyugai - you have the most experience with this 😄

I'll close this issue since it's best to talk about it inside the PR.
Cheers!