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/url_safe_token.py

@@ -0,0 +1,13 @@
+from itsdangerous import URLSafeTimedSerializer
+
+from notifications_utils.formatters import url_encode_full_stops
+
+
+def generate_token(payload, secret, salt):
+    return url_encode_full_stops(URLSafeTimedSerializer(secret).dumps(payload, salt))
+
+
+def check_token(token, secret, salt, max_age_seconds):
+    ser = URLSafeTimedSerializer(secret)
+    payload = ser.loads(token, max_age=max_age_seconds, salt=salt)
+    return payload