Add support for port forwarding for floating IPs

[simonre]

Port forwarding for floating IPs is not supported in gophercloud but it is a feature in OpenStack. This allows to reuse public IPs.

API:
https://developer.openstack.org/api-ref/network/v2/#show-port-forwarding

Source: https://github.com/openstack/neutron/blob/master/neutron/objects/port_forwarding.py

Schema: https://github.com/openstack/neutron/blob/master/neutron/db/models/port_forwarding.py

• Create
• List
• Get
• Update
• Delete

[simonre]

This is fully implemented now. ( #1651 , #1652 , #1688, #1698 , #1703 )

[jtopjian]

@simonre Thank you for your work on this! I apologize if it got off to a rough start. Your work is very much appreciated!

[simonre]

@jtopjian No worries at all, I think it's very enjoyable working with you! I'm just a bit slow with my PRs sometimes as I sometimes don't have too much time to work on them