I created a new group with the help of XML. 

    <record id="group_custom_manager" model="res.groups">
        <field name="name">Custom Manager</field>
        <field name="category_id" ref="base.module_category_hidden"/>
        <field name="users" eval="[(4, ref('base.user_root'))]"/>
    </record>

but in my case, after creating this group.  I have to manually enable the group for other users.  

Is it possible to enable this group for all users automatically??