home:
    path:     /
    methods:  [GET]
    defaults: { _controller: 'App\Controller\HomeController::indexAction' }

registration_register:
    path:     /register
    methods:  [GET, POST]
    defaults: { _controller: 'App\Controller\RegistrationController::registerAction' }

security_login:
    path:     /login
    methods:  [GET, POST]
    defaults: { _controller: 'App\Controller\SecurityController::loginAction' }

security_logout:
    path:    /logout

admin:
    resource: 'routes/admin.yaml'
    prefix: /admin

home:
    path:     /
    methods:  [GET]
    defaults: { _controller: 'App\Controller\HomeController::indexAction' }

registration_register:
    path:     /register
    methods:  [GET, POST]
    defaults: { _controller: 'App\Controller\RegistrationController::registerAction' }

security_login:
    path:     /login
    methods:  [GET, POST]
    defaults: { _controller: 'App\Controller\SecurityController::loginAction' }

security_logout:
    path:    /logout

admin:
    resource: 'routes/admin.yaml'
    prefix: /admin

admin_dashboard:
    path: /admin
    defaults:
        _controller: FrameworkBundle:Redirect:redirect
        route: admin_dashboard_index

Add route alias for admin_dashboard_index to point to /admin
Add route alias for admin_dashboard_index to point to /admin
