Replace marshmallow with jsonschema

Created a new schema that accepts request parameters for the
get_notifications v2 route.
Using that to validate now instead of the marshmallow validation.

Also changed the way formatted error messages are returned because
the previous way was cutting off our failing `enum` messages.

app/v2/notifications/notification_schemas.py

@@ -1,3 +1,4 @@
+from app.models import NOTIFICATION_STATUS_TYPES, TEMPLATE_TYPES
 from app.schema_validation.definitions import (uuid, personalisation)
 
 # this may belong in a templates module
@@ -72,6 +73,28 @@ get_notification_response = {
     ]
 }
 
+get_notifications_request = {
+    "$schema": "http://json-schema.org/draft-04/schema#",
+    "description": "schema for query parameters allowed when getting list of notifications",
+    "type": "object",
+    "properties": {
+        "status": {
+            "type": "array",
+            "items": {
+                "enum": NOTIFICATION_STATUS_TYPES
+            }
+        },
+        "template_type": {
+            "type": "array",
+            "items": {
+                "enum": TEMPLATE_TYPES
+            }
+        },
+        "older_than": uuid
+    },
+    "additionalProperties": False,
+}
+
 get_notifications_response = {
     "$schema": "http://json-schema.org/draft-04/schema#",
     "description": "GET list of notifications response schema",