[13.x] Add RouteKey and BindRoute attributes for route model binding

[Tresor-Kasenda]

This PR adds first-class PHP attribute metadata for implicit route model binding:

• #[RouteKey('field')] on Eloquent models
• #[BindRoute(parameter: ..., field: ..., withTrashed: ...)] on route parameters

This PR add :

• Reduce boilerplate for common getRouteKeyName() use cases.
• Allow per-parameter binding overrides directly at the route signature level.
• Keep attribute-based binding compatible with route caching.

Before / After

1) Model route key convention (RouteKey)

Before

class User extends Model
{
    public function getRouteKeyName(): string
    {
        return 'name';
    }
}

Route::get('/users/{user}', fn (User $user) => $user);

After

use Illuminate\Database\Eloquent\Attributes\RouteKey;

#[RouteKey('name')]
class User extends Model
{
    //
}

Route::get('/users/{user}', fn (User $user) => $user);

2) Per-parameter binding metadata (BindRoute)

Before

Route::get('/users/{user:name}', fn (User $user) => $user);

// No per-parameter override for trashed behavior.
// Only route-level withTrashed() is available.

After

use Illuminate\Routing\Attributes\BindRoute;

Route::get('/users/{user}', fn (#[BindRoute(field: 'name')] User $user) => $user);

Route::get('/users/{user}', fn (#[BindRoute(withTrashed: true)] User $user) => $user);

// Can opt-out per parameter, even if route is withTrashed().
Route::get('/users/{user}', fn (#[BindRoute(withTrashed: false)] User $user) => $user)
    ->withTrashed();

[shaedrich]

While I think that #[RouteKey] is tremendously helpful, I'm not so sure about #[BindRoute]:

• when used with field, it's actually quite a lot of boilerplate compared to {user:name}
• withTrashed would be interesting, but I would prefer this not to be tied to soft deletes in particular but to any scope. This would be very helpful and would eliminate the need for calling loadMissing() first thing in the controller when you need non-default relations

[taylorotwell]

Agree I would remove the BindRoute stuff.

[Tresor-Kasenda]

Thanks for the feedback.
{model:field} is indeed more concise for simple cases. #[BindRoute] mainly targets more complex scenarios (scopes, eager loading, constraints).

I also agree that a generic scope-based approach would be preferable over a soft-delete-specific withTrashed.

[Tresor-Kasenda]

@taylorotwell I can delete that and make another PR.