Using JwtAuthenticator in CakePHP's Authentication Plugin

JwtAuthentication.php

// to use the JwtAuthenticator in a CakePHP application you first have load the corresponding
// authenticator in your Application::getAuthenticationService(...)

$service->loadAuthenticator('Authentication.Jwt', [
  'returnPayload' => false 
]);

// The parameter 'returnPayload' is set to true by default - If you want your visitor using the JWT run trough a full authentication
// process, you should set it to false. 

// If you want to implement the full authentication process, you also have to
// load the identifier called 'JwtSubject'. You don't have to change any options here for default usage.

$service->loadIdentifier('Authentication.JwtSubject');

// To grant a visitor access to a protected page, you only have to put a query param named 'token' at the end of the URL which
// which contains the JWT you generated before. The validation process will run in the middleware automatically, but how to
// create such a JWT which can be processed by CakePHP? Sadly there's no information about that in the documentation, so let's
// go here...!

// The authentication plugin of CakePHP uses the PHP-JWT implementation from Firebase. The documentation there is kept
// very clearly and tells you everything you need to create a valid JWT.

use Cake\Utility\Security;
use Firebase\JWT\JWT; 

$payload = [
  IdentifierInterface::CREDENTIAL_JWT_SUBJECT => [
    'id' => $user->id
  ]
];

$jwt = JWT::encode($payload, Security::getSalt());

// The payload should only contain an array with the key specified by the authentication Plugin. This key points to an array
// containing only the ID (the primary key) of your Identity object. No more information are required to run through the authentication
// process. The JWT can be created in any controller.