Add support for defining Groups and Subgroups as enums

[lioneaglesolutions]

Problem

When defining groups and subgroups, it's nice to have a clear idea of what groups are available to use. PHP Backed Enums are a perfect way of achieving this. Otherwise, developers could mis-type group names easily such as;

#[Group('Users')];
#[Group('User')];  // typo

Solution

By allowing the usage of Backed Enums, it is very clean to be able to define your API Endpoint Groups as an enum;

enum EndpointGroup: string
{
    case Users = 'Users';
    case Invoices = 'Invoices';
}

Then in your codebase you can simply do;

#[Group(EndpointGroup::Invoices)]
class InvoiceController
{
   // ...
}

Alternative

An alternative could be to just add ->value to each enum which would not require any codebase changes however this is not visually pleasing and not as nice of a DX as being able to pass an enum directly.

#[Group(EndpointGroup::Invoices->value)]
class InvoiceController
{
   // ...
}

[shalvah]

Nice convenience feature!

[shalvah]

Ugh, I really hate these property accessor methods.

Considering making the next major PHP 8.4 only so I can do this with property hooks.

(I won't do that.)