A database-less user provider
=============================

From [jwt.io](https://jwt.io/introduction):

> Self-contained: The payload contains all the required information about the user, avoiding the need to query the database more than once.
> https://jwt.io/introduction

A JWT is _self-contained_, meaning that we can trust into its payload for processing the authentication. 
In a nutshell, there should be no need for loading the user from the database when authenticating a JWT Token,  
the database should be hit only once for delivering the token. 

That's why we decided to provide a user provider which is able to create User instances from the JWT payload.

Configuring the user provider
-----------------------------

To work, the provider just needs a few lines of configuration:

```yaml
# config/packages/security.yaml
security:
    providers:
        jwt:
            lexik_jwt: ~
```

Then, use it on your JWT protected firewall:

```yaml
security:
    firewalls:
        api:
            provider: jwt
            guard:
                # ...
```

What does it change?
--------------------

Now that the provider is configured, it will automatically be used by the `JWTGuardAuthenticator` when authenticating a token.
Instead of loading the user from a "datastore" (i.e. memory or any database engine), a `JWTUserInterface` instance will be created from the JWT payload, will be cached for a request and be authenticated.
We provide a simple  `JWTUser` class implementing this interface, which is used by default when configuring the provider.

Can I use my own user class?
----------------------------

Of course, you can. You just need to make your user class implement the `JWTUserInterface` interface.
This interface contains only a `createFromPayload()` _named constructor_ which takes the user's username and 
the JWT token payload as arguments and returns an instance of the class.

##### Sample implementation

```php
namespace App\Security;

final class User implements JWTUserInterface
{
    // Your own logic
    
    public function __construct($username, array $roles, $email)
    {
        $this->username = $username;
        $this->roles = $roles;
        $this->email = $email;
    }
    
    public static function createFromPayload($username, array $payload)
    {
        return new self(
            $username,
            $payload['roles'], // Added by default
            $payload['email']  // Custom
        );
    }
}
```

_Note_:  You can extend the default `JWTUser` class if that fits your needs.

##### Configuration

```yaml
# config/packages/security.yaml
providers:
    # ...
    jwt:
        lexik_jwt:
            class: App\Security\User
```

And voilà!