Replace how .load is called

https://marshmallow.readthedocs.io/en/stable/upgrading.html#schemas-are-always-strict

`.load` doesn't return a `(data, errors)` tuple any more - only data is
returned. A `ValidationError` is raised if validation fails. The code
now relies on the `marshmallow_validation_error` error handler to handle
errors instead of having to raise an `InvalidRequest`. This has no
effect on the response that is returned (a test has been modified to
check).

Also added a new `password` field to the `UserSchema` so that we don't
have to specially check for password errors in the `.create_user` endpoint
- we can let marshmallow handle them.

app/job/rest.py

@@ -79,7 +79,7 @@ def cancel_letter_job(service_id, job_id):
 
 @job_blueprint.route('/<job_id>/notifications', methods=['GET'])
 def get_all_notifications_for_service_job(service_id, job_id):
-    data = notifications_filter_schema.load(request.args).data
+    data = notifications_filter_schema.load(request.args)
     page = data['page'] if 'page' in data else 1
     page_size = data['page_size'] if 'page_size' in data else current_app.config.get('PAGE_SIZE')
     paginated_notifications = get_notifications_for_job(
@@ -173,7 +173,7 @@ def create_job(service_id):
 
     data.update({"template_version": template.version})
 
-    job = job_schema.load(data).data
+    job = job_schema.load(data)
 
     if job.scheduled_for:
         job.job_status = JOB_STATUS_SCHEDULED