2.0 IPAM Overhaul: Add constraints to Prefix.parent

[gsnider2195]

• Prefix type network can only contain IP addresses and prefix of type pool
• Prefix type container can only contain child prefixes of type container or network
• Prefix type is user serviceable and defaults to Container
• Bring back the is_pool property
• IP Address parent property cannot be set to a prefix with type pool, it will parent to the nearest network prefix
• Pools cannot contain child prefixes or ip addresses

This is going to require us to revisit the IPAM data migrations for prefix/ip address parenting

TODO: UX fixes

Prefix save/delete methods

• Network contains IP addresses but we want to subdivide the network (/24 converted to /25)
  • Newly created prefix will contain all of the parent prefix's IP addresses, parent will be converted to a container automatically
  • Newly created prefix will NOT contain all of the parent prefix's IP addresses. Do we fail on creation of the new prefix?
• Network contains IP addresses but we want to delete the network and reparent all of the IPs to the parent (/25 converted to /24)

IP Address save method

• IP Address created in a container prefix that does not contain any prefixes. Does the creation of the IP address automatically convert the parent container to a network?

[gsnider2195]

Completed by #3942