title: Symfony 4 - EasyAdmin Bundle - default form value
body: <hr>
  
  <p>Hello everyone !</p>
  
  <p>I'm using easyadmin for a project and i'm a bit confuse.
  I have a User entity with roles "ROLE_CUSTOMER" and "ROLE_REPAIRMAN". 
  I can display and add users depend on their roles :</p>
  
  <p>entities.yaml : </p>
  
  <pre><code>easy_admin:
    entities:
      Customer:
        label: 'Customer'
        class: App\Entity\User
        list:
          dql_filter: "entity.roles LIKE '%%ROLE_CUSTOMER%%'"
        form:
          title: "Add Customer"
          fields: &amp;userFormFields
            - { property: 'email' }
            - { property: 'civility' }
            - { property: 'lastname' }
            - { property: 'firstname' }
            - { property: 'phone' }
            - { property: 'mobile' }
      Repairman:
        label: 'Repairman'
        class: App\Entity\User
        controller: App\Controller\Admin\RepairmanController
        list:
          dql_filter: "entity.roles LIKE '%%ROLE_REPAIRMAN%%'"
          fields:
            - id
            - company
            - email
            - civility
            - firstname
            - lastname
            - { property: 'isAdminGroup' }
        form:
          title: "Add Repairman"
          fields:
            - { property: 'email' }
            - { property: 'civility' }
            - { property: 'lastname' }
            - { property: 'firstname' }
            - { property: 'phone' }
            - { property: 'mobile' }
            - { property: 'company' }
            - { property: 'vitrage' }
            - { property: 'kbis' }
            - { property: 'siret' }
            - { property: 'isAdminGroup' }
  </code></pre>
  
  <p>menu.yaml</p>
  
  <pre><code>easy_admin:
    design:
      menu:
        - label: 'Clients'
          icon: 'users'
          entity: 'Customer'
          children:
            - { label: 'Show', entity: 'Customer', params: { action: 'list' } }
            - { label: 'Add', entity: 'Customer', params: { action: 'new' } }
        - label: 'Repairman'
          icon: 'users'
          entity: 'Repairman'
          children:
            - { label: 'Show', entity: 'Repairman', params: { action: 'list' } }
            - { label: 'Add', entity: 'Repairman', params: { action: 'new' } }
  </code></pre>
  
  <p>When I click on add a customer, I would like his role to be ROLE_CUSTOMER and when I click on add a repairman, his role to be ROLE_REPAIRMAN</p>
  
  <p>I tried to extend the AdminController, the RepairmanController but I can't get what I want. I also tried to set a default value using : </p>
  
  <pre><code>- { property: 'roles', type: 'hidden', type_options: { empty_data: "['ROLE_REPAIRMAN']" } }
  </code></pre>
  
  <p>Here I have an error because he needs an array and he interprets the value as a string.</p>
  
  <p>Can someone help me to figure it out please ? Or do you have a better solution ?</p>
  
  <p>Thank you !</p>