Add new resource for port bindings

As a result of implementing providing Nova port binding information for
live migration [1], a new resource for callbacks is required. This
resource will be used by the multiple port binding service plugin [2]
to notify the core plugin and other subscribers when create, update and
delete operations are performed on a port binding.

[1] https://review.openstack.org/#/c/460021
[2] https://review.openstack.org/#/c/414251

Related-Bug: #1580880

Change-Id: Ibbc7af67cf1282cbf7d9d3a681b9a04a7922c24a

neutron_lib/callbacks/resources.py

@@ -17,6 +17,7 @@ NETWORK = 'network'
 NETWORKS = 'networks'
 PORT = 'port'
 PORTS = 'ports'
+PORT_BINDING = 'port_binding'
 PORT_DEVICE = 'port_device'
 PROCESS = 'process'
 ROUTER = 'router'

releasenotes/notes/add-port-binding-resource-73f9800dbda121ca.yaml

@@ -0,0 +1,7 @@
+---
+features:
+  - A new ``PORT_BINDING`` resource definition has been added to
+    ``neutron_lib.callbacks.resources``, to enable the multiple port
+    binding service plugin to notify the core plugin and other
+    subscribers when create, update and delete operations are performed
+    on a port binding.