[8.x] Add types for casting encrypted strings to objects

[jasonmccreary]

Per the discussion in #34937, this is a fast-follow PR to add "types" or "formats" to specify additional casts for encrypted attributes.

This allows you to persist complex types like arrays, json, objects, or collections as encrypted values, while working with them naturally within your application.

Example:

public $casts = [
    'user_ids' => 'encrypted:array',
    'preferences' => 'encrypted:json',
    'payment_method' => 'encrypted:object',
    'dependents' => 'encrypted:collection',
];

I feel this rounds out this feature by covering the most common use cases. For anything more, a custom cast may be used.

Note: Since these are stored encrypted, you will most like want to use a text field for any attributes using these casts.

[jasonmccreary]

@taylorotwell, please make my cascading comment beautiful 😅

[tontonsb]

It has been mentioned before — the real solution would be chainable casts.

But I understand. I've done exactly the same in my own package and even support all of the default Eloquent typecasts on decryption.

[hotmeteor]

@jasonmccreary @tontonsb

I've put together a PR to support chained/chainable casts. Wondering if it might be worth considering this option rather than adding more cast rules?

#34963