Neutron -> Designate integration does not consider the dns pool for zone

[Dmitry Galkin]

Hi,

We're using Neutron-> Designate "Reverse" Integration: https://docs.openstack.org/designate/latest/contributor/integrations.html
for creating the PTR records automatically for FloatingIPs.

The reverse dns zone for PTR gets created always in the default Designate server pool.

We have multiple dns server pools and the expectation is that if the forward DNS zone (where A record is auto-created) is hosted on the non-default Designate pool, than the reverse dns zone should also be created on the same Designate pool.

This is the code which handles zone creation: https://github.com/openstack/neutron/blob/master/neutron/services/externaldns/drivers/designate/driver.py#L121-L126

It can be improved as follows:

1. Ask Designate on which dns pool the forward dns zone is located (https://github.com/openstack/neutron/blob/master/neutron/services/externaldns/drivers/designate/driver.py#L93 -> this is where A is created)

2. If that is not a default dns pool -> specify that pool uuid as an attribute when creating the reverse dns zone for PTR records.