<doctrine-mongo-mapping xmlns="http://doctrine-project.org/schemas/odm/doctrine-mongo-mapping"
                        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                        xsi:schemaLocation="http://doctrine-project.org/schemas/odm/doctrine-mongo-mapping
                    http://doctrine-project.org/schemas/odm/doctrine-mongo-mapping.xsd">

    <document name="Integrated\Bundle\ContentBundle\Document\ContentType\ContentType" collection="content_type">

        <field fieldName="id" id="true" strategy="NONE" unique="true" />
        <field fieldName="class" type="string" />
        <field fieldName="name" type="string" />
        <field fieldName="options" type="hash" />
        <field fieldName="createdAt" type="date" />

        <embed-many field="fields">
            <discriminator-map>
                <discriminator-mapping value="default" class="Integrated\Bundle\ContentBundle\Document\ContentType\Embedded\Field" />
                <discriminator-mapping value="custom" class="Integrated\Bundle\ContentBundle\Document\ContentType\Embedded\CustomField" />
            </discriminator-map>
            <default-discriminator-value value="default" />
        </embed-many>

    </document>

</doctrine-mongo-mapping>
<doctrine-mongo-mapping xmlns="http://doctrine-project.org/schemas/odm/doctrine-mongo-mapping"
                        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                        xsi:schemaLocation="http://doctrine-project.org/schemas/odm/doctrine-mongo-mapping
                    http://doctrine-project.org/schemas/odm/doctrine-mongo-mapping.xsd">

    <document name="Integrated\Bundle\ContentBundle\Document\ContentType\ContentType" collection="content_type">

        <field fieldName="id" id="true" strategy="NONE" />
        <field fieldName="class" type="string" />
        <field fieldName="name" type="string" />
        <field fieldName="options" type="hash" />
        <field fieldName="createdAt" type="date" />

        <embed-many field="fields">
            <discriminator-map>
                <discriminator-mapping value="default" class="Integrated\Bundle\ContentBundle\Document\ContentType\Embedded\Field" />
                <discriminator-mapping value="custom" class="Integrated\Bundle\ContentBundle\Document\ContentType\Embedded\CustomField" />
            </discriminator-map>
            <default-discriminator-value value="default" />
        </embed-many>

    </document>

</doctrine-mongo-mapping>
Remove unique="true" on id field
Remove unique="true" on id field
