Comment 6 for bug 1773377

As discussed with Pedro on IRC, what we could do is:

* create dns-provider relations between neutron-{openvswitch,gateway} and designate-bind to export designate-bind endpoints to the neutron-related charms - this will allow us to bind this "dns-provider" endpoint to a space on the designate-bind side (no need for extra-bindings) and provide values to configure dnsmasq via the dhcp agent .ini file with designate-bind IP addresses only known after the deployment (especially since we deploy designate-bind into containers that get addresses allocated dynamically);
* document a requirement that network engineers should route traffic from provider network subnets to a network space used in "dns-provider" endpoint binding;
* document a requirement that for recursion ACLs to be populated operators need to reconfigure designate-bind according to provider network subnets that will be used.

This approach allows us to avoid requiring deployers/operators to configure dns-servers at the post-deployment stage due to dynamic LXD IP address allocations. Provider network subnets for ACLs, on the other hand, can be present at the design stage and placed into bundles before the deployment.

This removes the need for post-deployment actions which is what we are trying to achieve here.