title: JWTRefreshTokenBundle change user_identity_field
body: <p>I use jwt token for auth and I had to change <code>user_identity_field</code> to email. And after that when I try call <code>/api/token/refresh</code> I have 401 status code. Because for refresh token entity in <code>username</code> property saved username data from user </p>
  
  <p>my config </p>
  
  <pre><code>lexik_jwt_authentication:
  private_key_path: '%jwt_private_key_path%'
  public_key_path:  '%jwt_public_key_path%'
  pass_phrase:      '%jwt_key_pass_phrase%'
  token_ttl:        '%jwt_token_ttl%'
  user_identity_field: email
  
  gesdinet_jwt_refresh_token:
  ttl: '%jwt_refresh_token_ttl%'
  ttl_update: true
  user_provider: security.user.provider.concrete.chain_provider
  </code></pre>
  
  <p>and my security </p>
  
  <pre><code>security:
  encoders:
      AppBundle\Entity\User:
          algorithm: bcrypt
  
      AppBundle\Entity\Admin:
          algorithm: bcrypt
  
  providers:
      chain_provider:
          chain:
              providers: [admins, entity_provider]
  
      admins:
          entity:
              class: AppBundle:Admin
              property: email
  
      entity_provider:
          entity:
              class: AppBundle:User
              property: email
  
  firewalls:
      dev:
          pattern: ^/(_(profiler|wdt)|css|images|js)/
          security: false
  
      refresh:
          pattern:  ^/api/token/refresh
          stateless: true
          anonymous: true
  
      api_admin:
          pattern:   ^/api/admin
          stateless: true
          anonymous: false
          provider: chain_provider
          guard:
              authenticators:
                  - app.jwt_token_authenticator
  
      login:
          pattern:  ^/api/login
          stateless: true
          anonymous: true
          form_login:
              check_path: /api/login_check
              require_previous_session: false
              username_parameter: _email
              password_parameter: _password
              success_handler: custom
              failure_handler: lexik_jwt_authentication.handler.authentication_failure
  </code></pre>
  
  <p>now <code>/api/token/refresh</code> I have response </p>
  
  <pre><code>{
    "code": 401,
    "message": "Bad credentials"
  }
  </code></pre>
  
  <p>because <code>\Gesdinet\JWTRefreshTokenBundle\Entity\RefreshToken</code> have <code>username</code> data from user, but in my config for <code>lexik_jwt_authentication</code> I changed it </p>
  
  <pre><code>user_identity_field: email
  </code></pre>
  
  <p>How to apply <code>user_identity_field: email</code> to refresh token ? </p>