Localize notification_utils to the admin

This changeset pulls in all of the notification_utils code directly into the admin and removes it as an external dependency. We are doing this to cut down on operational maintenance of the project and will begin removing parts of it no longer needed for the admin.

Signed-off-by: Carlo Costino <carlo.costino@gsa.gov>

notifications_utils/serialised_model.py

@@ -0,0 +1,61 @@
+from abc import ABC, abstractmethod
+
+
+class SerialisedModel(ABC):
+    """
+    A SerialisedModel takes a dictionary, typically created by
+    serialising a database object. It then takes the value of specified
+    keys from the dictionary and adds them to itself as properties, so
+    that it can be interacted with like any other object. It is cleaner
+    and safer than dealing with dictionaries directly because it
+    guarantees that:
+    - all of the ALLOWED_PROPERTIES are present in the underlying
+      dictionary
+    - any other abritrary properties of the underlying dictionary can’t
+      be accessed
+
+    If you are adding a new field to a model, you should ensure that
+    all sources of the cache data are updated to return that new field,
+    then clear the cache, before adding that field to the
+    ALLOWED_PROPERTIES list.
+    """
+
+    @property
+    @abstractmethod
+    def ALLOWED_PROPERTIES(self):
+        pass
+
+    def __init__(self, _dict):
+        for property in self.ALLOWED_PROPERTIES:
+            setattr(self, property, _dict[property])
+
+
+class SerialisedModelCollection(ABC):
+    """
+    A SerialisedModelCollection takes a list of dictionaries, typically
+    created by serialising database objects. When iterated over it
+    returns a model instance for each of the items in the list.
+    """
+
+    @property
+    @abstractmethod
+    def model(self):
+        pass
+
+    def __init__(self, items):
+        self.items = items
+
+    def __bool__(self):
+        return bool(self.items)
+
+    def __getitem__(self, index):
+        return self.model(self.items[index])
+
+    def __len__(self):
+        return len(self.items)
+
+    def __add__(self, other):
+        return list(self) + list(other)
+
+    def __radd__(self, other):
+        return list(other) + list(self)