Different filename formats per document type

[jgillula]

It would be great if I could set different filename formats (like PAPERLESS_FILE_FORMAT) for each document type.

My use case is that I have a hierarchy of document types, and I want the organization of files on disk to reflect this. For example, I have

[paperless_root]/Financial Documents/Banking Documents/[Bank Name]/[filename]
[paperless_root]/Financial Documents/Pay Statements/[Employer]/[filename]
[paperless_root]/Business Services/[Business]/[filename]
[paperless_root]/Receipts/[Store]/[filename]

AFAICT there's currently no way to accomplish this with a global PAPERLESS_FILENAME_FORMAT.

Of course, if the document has no type, or the per document type filename format has not been set, then it would fall back to the default global PAPERLESS_FILENAME_FORMAT.

I can code, so I'm willing to try to implement this and make a pull request. Of course I want to implement something that the maintainers would want/accept, so I'm curious if this is something you'd be interested in. (And if it is something you'd be interested in, I'd be happy to iterate on the design here before I start coding, so that what I write has a greater chance of being accepted.)

Thanks for the awesome project!