- add function to get reference from filename
- add function to move pdf from scan folder to process folder
- add function to delete pdfs from scan bucket for failed virus scans
* Added is_precompiled_letter method to letter/utils.py
* Added tests for letter/utils.py
* Added tests for the rest endpoint
* Moved the Precompiled name to a central location
* Added hidden field to the test method to create a template
Pre-compiled letter endpoint uploads PDF contents to S3 directly
instead of creating a letter task to generate PDF using template
preview.
This moves some of the utility functions used by existing letter
celery tasks to app.letters.utils, so that they can be reused by
the API endpoint.