Support templating of single-client pdf file names

[jangevaare]

Seeing as file may be attached to emails for digital delivery, we may wish as part of this pipeline support templating of filenames, like how is done for qr codes and encryption passwords.

It could be done as a standalone step as well, or just done as part of the email step - doesn't necessarily need to be a refactor of existing pipeline steps to support

[jangevaare]

This would require filenames with templating are guaranteed to be unique based on current pipeline, so we may need to add a short hash or something to ensure that can be guranteed/reduce collisions, in addition to erroring when it happens anyways.