Symfony - Création d'un espace sécurisé (Config)

security.yml

security:
    encoders:
        Symfony\Component\Security\Core\User\User: plaintext

    providers:
        in_memory:
            memory:
                users:
                    admin:
                        password: "PASSWORD123"
                        roles: 'ROLE_ADMIN'

    firewalls:
        dev:
            pattern: ^/(_(profiler|wdt)|css|images|js)/
            security: false

        admin:
            provider: in_memory
            pattern: ^/admin
            form_login:
                login_path: login
                check_path: login_check
                default_target_path: admin
            logout:
                path: logout
                target: homepage

        main:
            anonymous: ~

    access_control:
        admin:
            path: ^/admin
            roles: ROLE_ADMIN