XML mapping for Doctrine MongoDB ODM References Extension

[webdevilopers]

Coming from:

• Add XML mapping example for References doctrine-extensions/DoctrineExtensions#1564 (comment) @l3pp4rd
• ODM double properties for ORM mapping doctrine-extensions/DoctrineExtensions#750 (comment) @stof
• https://twitter.com/webdevilopers/status/720290618249912320

I never got it working on the Document side - don't know if the XML mapping is complete anyway:

http://atlantic18.github.io/DoctrineExtensions/schemas/orm/doctrine-extensions-3.0.xsd

namespace Acme\AppBundle\Entity;

class Customer
{
    /**
     * @Gedmo\ReferenceMany(type="document", class="Acme\DomainModel\Order", mappedBy="customer")
     */
    private $orders;
}

        <field fieldName="customerId" type="integer" />
        <gedmo:reference type="entity"
             class="Acme\AppBundle\Entity\Customer"
             inversed-by="orders" identifier="customerId" />

namespace Acme\DomainModel;

class Order
{
    private $customer;
    private $customerId;
}