Adjust API Endpoints for Task Links

This should enable API support for links to resources related to tasks.

Change-Id: I91cf3c877d717abfa25983d64ea03ead393f4816

storyboard/api/v1/wmodels.py

@@ -205,6 +205,9 @@ class Task(base.APIBase):
     story_id = int
     """The ID of the corresponding Story."""
 
+    link = wtypes.text
+    """A related resource for this task."""
+
     project_id = int
     """The ID of the corresponding Project."""