social/mail_restrict_follower_selection/data/ir_config_parameter.xml

<?xml version="1.0" encoding="UTF-8"?>
<odoo noupdate="1">
    <record id="parameter_domain" model="ir.config_parameter">
        <field name="key">mail_restrict_follower_selection.domain</field>
        <field name="value">[('customer', '=', True)]</field>
    </record>
</odoo>