Add support for configurable role identifier key (e.g., slug)

[philiplamb]

I needed to use a slug (explicitly not use "name" column), and to check against it, but this package forces you to use the name in your checkRole methods. I also saw many issues asking for slug support, this doesn't add slug so I made this configurable through the config/permission.php.

#1846

You can now update this line to use your preferred column:
'role_identifier' => 'name', // e.g., change to 'slug'

This PR:

• Updates role matching methods (hasRole, hasAllRoles, hasExactRoles, etc.) to respect the configured identifier.
• Adds a getRoleKey() helper method to the HasRoles trait.
• Introduces findByKey() in the Role model to support lookup by the configured identifier.
• Tests name and slug usage. I had to add slug for testing as nullable.
• Has backward compatibility. The default behavior (name) remains unchanged.

[parallels999]

Has backward compatibility.
Introduces findByKey() in the Role

Not, it breaks it, spatie/laravel-permission/Contracts/Role.php
It also breaks other things, but why go into details, hehe
getRoleKey seems like a key, really ambigous, same findByKey

[philiplamb]

Hi @parallels999 , thanks for your feedback, i fixed the naming and some mistakes. I'd appreciate if you'd go into more details, or i need to do something else. This is my first PR. Thank you.

[drbyte]

I needed to use a slug (explicitly not use "name" column), and to check against it

In cases like this, instead of making broad package changes, I typically just use the slug to lookup the model ID, and then explicitly pass the model to all the corresponding functions. No performance hit because lookups of role-related details are user-initiated, not pageload-initiated.