What is the default policy for nova , keystone , etc when nova policy.json is empty and how to edit policy.json in Red Hat OpenStack Platform 10 and later

Issue

• The /etc/nova/policy.json file is empty after a default installation of OpenStack Platform 10 and later. The only thing in this file is empty brackets"{}"

• undercloud default policy.json

[root@instack ~]# grep ^[^#] /etc/nova/policy.json
{
}
[root@instack ~]#

• Overcloud default policy.json

[root@overcloud-controller-0 ~]# grep ^[^#] /etc/nova/policy.json
{
}
[root@overcloud-controller-0 ~]#

• What is the default policy for nova?