title: Displaying data from a normalised m-m relationship
body: <p>I have have 2 tables, ServiceProvider , Entity. There is a m-m relationship between them so I created a link table spEntity which contains the foreign keys from both the other tables.</p>
  <p>I have backpack working fine on the 3 tables separately, I use the relationship type on the spEntity CRUD to show the names from the other 2 tables and this all works fine.</p>
  <p>However, what I would like to do is when the ServiceProvider record is being created</p>
  <ul>
  <li>show a list of all the entities</li>
  <li>allow the user to select one and then when the save button is pressed</li>
  <li>create the spEntity record.</li>
  </ul>
  <p>I have tried</p>
  <pre><code>protected function setupCreateOperation()
  {
      CRUD::setValidation(ServiceProviderRequest::class);
  
      CRUD::field('ServiceProviderName');
      CRUD::field('ServiceProviderEmailAddress');
      CRUD::field('ServiceProviderDescription');
      CRUD::addfield(['name'=&gt;'Entity',
                      'type'=&gt;'relationship',
                      'attribute' =&gt; 'EntityName',
                      'pivot'=&gt;true,
                      'relation_type'=&gt;'belongstomany'
          ]);
  }
  </code></pre>
  <p>but I get the error :
  BadMethodCallException  PHP 8.1.7   9.19.0
  Method Backpack\CRUD\app\Library\CrudPanel\CrudPanel::relationAllowsMultiple does not exist.</p>
  <p><a href="https://i.stack.imgur.com/emxWK.png" rel="nofollow noreferrer">Table relations</a></p>
  <p>Is this possible?</p>