<?xml version="1.0"?>

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Api/etc/extension_attributes.xsd">
<extension_attributes for="Magento\Customer\Api\Data\CustomerInterface">
    <attribute code="phone_number" type="string"/>
</extension_attributes>

</config>