Laravel Passport gives me "Invalid key supplied"

Title: Laravel Passport and Multi-Tenant Applications: An In-Depth Guide for Troubleshooting "Invalid Key Supplied" Issues Body:

If you've been working on a Laravel multi-tenant application with Laravel Passport and TanancyForLaravel, you may have encountered the "Invalid key supplied" error. This error can be frustrating as it prevents authentication and leads to a poor user experience. Let us delve deeper into this issue and explore potential solutions.

Firstly, ensure your authentication configuration is correct for each tenant. In Laravel's config/auth.php, you might have multiple authentication types defined under 'guards'. For your multi-tenant application, define separate guards based on the database you want to query. This should be done through the following code snippet:

'guards' => [
        'webTenant1' => [ // Change this depending on your tenant names
            'driver' => 'session',
            'provider' => 'tenant_users',
        ],
        'webTenant2' => [ // Same as before - change to match your tenants
            'driver' => 'passport',
            'model' => 'tenants_users',
        ],
    ],

Alternatively, you might have defined the guards in a different manner. Nonetheless, ensure that your guard definitions are tailored to your tenant databases.

Next, check if you're using the correct authentication drivers and providers. In Laravel's Controllers/AuthController.php, the authentication method may call upon a specific driver or provider. If these do not align with your existing guards configuration, modify them accordingly.

Another possible cause could be duplicate or missing Passport keys in your tenants' databases. To prevent this issue from occurring, follow TenancyForLaravel documentation and create separate keys for each tenant in the database seeder class. Ensure that these keys are generated manually instead of using the passport:install command. Create clients manually for each tenant as well:

public function run()
{
    $client = new ClientRepository();
    // Create Password Grant Clients and Personal Access Clients for your tenants
    foreach (Tenant::all() as $tenant) {
        $client->createPasswordGrantClient(null, 'Default password grant client', 'http://your.redirect.path', $tenant->id);
        $client->createPersonalAccessClient(null, 'Default personal access client', 'http://your.redirect.path', $tenant->id);
    }
}

In your application's configuration file, set the tenant database seeder class in the config/tenancy.php file at the key 'seeder_parameters'. Ensure that you have seeded the database for all tenants and generated keys through the aforementioned process.

To generate the Passport keys for your application, run the command: php artisan passport:keys. This will create a single key pair for your Laravel application. Finally, run your tests to ensure the application is properly authenticating with each tenant database and the error "Invalid Key Supplied" no longer occurs.

In summary, the "Invalid Key Supplied" error in multi-tenant applications using Laravel Passport can be caused by incorrect authentication configurations or duplicate/missing keys. By ensuring that your guards, drivers, providers, and tenant database seeding are correct, you should be able to tackle this issue effectively.