Add a WSME model for attachments

Change-Id: I8369f7b9ad6c4f8c7807adcac3a13e88db21f0c9

storyboard/api/v1/wmodels.py

@@ -1,5 +1,6 @@
 # Copyright (c) 2014 Mirantis Inc.
 # Copyright (c) 2016 Codethink Ltd
+# Copyright (c) 2019 Adam Coldrick
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -366,6 +367,31 @@ class Task(base.APIBase):
             due_dates=[1, 2, 3])
 
 
+class Attachment(base.APIBase):
+    """Represents metadata about a file attachment."""
+
+    name = wtypes.text
+    """The name of this attachment."""
+
+    link = wtypes.text
+    """The link to the actual attachment for download."""
+
+    creator_id = int
+    """The ID of the user who created this attachment."""
+
+    story_id = int
+    """The story that this attachment is related to."""
+
+    @classmethod
+    def sample(cls):
+        return cls(
+            name="logs.tar",
+            link="https://example.org/v1/AUTH_test/storyboard/logs.tar",
+            creator_id=1,
+            story_id=1
+        )
+
+
 class Branch(base.APIBase):
     """Represents a branch."""