This continues the work from Template Preview [1], so that we have
a complete store of original PDFs to use for testing changes to it.
Previously we did store some originals, but these were only invalid
PDFs that had failed sanitisation; for valid PDFs, the "transient"
bucket only contains the sanitised versions, which the API deletes
/ moves when the notification is sent [2].
Since the notification is only created at a later stage [3], there's
no easy way to get the final name of the PDF we send to DVLA. Instead,
we use the "upload_id", which eventually becomes the notification ID
[4]. This should be enough to trace the file for specific debugging.
Note that we only want to store original PDFs if they're valid (and
virus free!), since there's no point testing changes with bad data.
[1]: https://github.com/alphagov/notifications-template-preview/pull/545
[2]: c44ec57c17/app/service/send_notification.py (L212)
[3]: 7930a53a58/app/main/views/uploads.py (L362)
[4]: 7930a53a58/app/main/views/uploads.py (L373)
We have lots of functions for converting various types of data into
strings to be displayed to the user somewhere.
This commit collects all these functions into their own module, rather
than having them cluttering up `app/__init__.py` or buried amongst
various other things that have ended up in `app/utils.py`.
the upload preview page has a file_id - this corresponds to the file in
the transient pdf uploads bucket. However, if the user already hit send
(and then navigated back) the file's no longer in that bcuket, it's been
moved to the regular letters-pdf bucket. So the s3 get request fails. To
avoid this, simply redirect to the notifications page if the file isn't
in the transient bucket. This is better for the user as it'll stop them
trying to submit it twice, and will provide more clarity on the status
of the notification too.
