WIP: Adding VLAN ID to Port objects via Tags

Adds a module to store and retrieve VLAN IDs using Tags on the Port
model. Also, VLAN ID data is attached to Port descriptions, where
appropriate,  obtained via port show API requests.

Along with necessary unit tests.

quark/plugin_views.py

@@ -23,6 +23,7 @@ from oslo_log import log as logging
 
 from quark.db import ip_types
 from quark import network_strategy
+from quark import port_vlan_id
 from quark import protocols
 
 
@@ -179,6 +180,11 @@ def _port_dict(port, fields=None):
     # NOTE(mdietz): more pythonic key in dict check fails here. Leave as get
     if port.get("bridge"):
         res["bridge"] = port["bridge"]
+
+    vlan_id = port_vlan_id.retrieve_vlan_id(port)
+    if vlan_id:
+        res["vlan_id"] = vlan_id
+
     return res