Update the resultset to relect how users will consume the information.

- Do not show "hidden" or precompiled templates, users don't know about them.
- Remove the client reference if it is the file name of an uploaded file.
- Format the date for created_at
- Added a test for all the different types of letters.
 1) One off templated letter
 2) Letter created by a csv upload or job.
 3) Uploaded letter
 4) Templated letter sent by the API
 5) Precompiled letter sent by the API

app/dao/returned_letters_dao.py

@@ -74,6 +74,8 @@ def fetch_returned_letters(service_id, report_date):
             Template.name.label('template_name'),
             table.template_id,
             table.template_version,
+            Template.hidden,
+            table.api_key_id,
             table.created_by_id,
             User.name.label('user_name'),
             User.email_address,