Create is_event_delete function for resources

Not all resources are marked to be deleted by adding
a deleted_at attribute, this change will allow for doing
this check on a per-resource basis.

Change-Id: I2759038233b4a54661cd8a5fe76c8cb4e983d15d

atmosphere/models.py

@@ -197,7 +197,7 @@ class Resource(db.Model, GetOrCreateMixin):
             raise exceptions.EventTooOld()
 
         # If we're deleted, then we close the current period.
-        if 'deleted_at' in event['traits']:
+        if resource.__class__.is_event_delete(event):
             period.ended_at = event['traits']['deleted_at']
         elif period.spec != spec:
             period.ended_at = event['generated']
@@ -259,6 +259,11 @@ class Instance(Resource):
 
         return False
 
+    @classmethod
+    def is_event_delete(cls, event):
+        """is_event_delete"""
+        return 'deleted_at' in event['traits']
+
 
 class BigIntegerDateTime(TypeDecorator):
     """BigIntegerDateTime"""

atmosphere/tests/unit/test_models.py

@@ -428,6 +428,15 @@ class TestResource(GetOrCreateTestMixin):
 
 @pytest.mark.usefixtures("db_session")
 class TestInstance:
+    def test_is_event_delete(self):
+        event = fake.get_normalized_event()
+        assert models.Instance.is_event_delete(event) == False
+
+    def test_is_event_delete_for_actual_delete(self):
+        event = fake.get_normalized_event()
+        event['traits']['deleted_at'] = event['generated']
+        assert models.Instance.is_event_delete(event) == True
+
     def test_is_event_ignored(self):
         event = fake.get_normalized_event()
         assert models.Instance.is_event_ignored(event) == False