Add Capabilities to Process and Smash Externally Supplied Data

### Context

It's quite likely that there will be researchers who will want to combine `refine.bio`-provided data with their own private data repositories.

It'd be great if we provided some functionality to make this easier for them by either running through our processors, gene-converters and smasher. Off the top of my head, I'm imagining that this could be new management command to live inside a processor/smasher Dockerfile and a small script with documentation to wire everything up together. But I'm certainly open to suggestions here!

This would also improve our own testing abilities.

### Problem or idea

I think this could be a good project for @Willv19 to take on if @kurtwheeler doesn't have a grander plan in mind.

### Solution or next step

Next step would probably to put some bounds on the requirements here - what kind of private data is a researcher most likely to have? Will it need to be processed, or just gene-conversion, or even just smashing?

Start by defining the private-data use cases and whether processing, gene conversion, smashing, or all three are required. Then inspect the processor and smasher Dockerfiles, existing management commands, and related scripts; done means a bounded implementation with a documented, runnable workflow and tests for the supported path.

Written by the indexing model from the issue text.