* DEV: Implement uploads command entrypoint
- Setup Thor UploadsCommand for CLI
- First pass at modularizing various parts of the exising `uploads_import` script
* DEV: First attempt at modularizing missing uploads fixer task
Move missing upload fix to a dedicated uploads task implementation unit
* DEV: First attempt at modularizing missing uploads uploader task
Move uploader to a dedicated uploads task implementation unit
* DEV: First attempt at modularizing missing uploads optimizer task
Move optimizer to a dedicated uploads task implementation unit
* DEV: Various follow up fixes to get optimization working
- Start threads early
- Improve "log" message formatting
- Add missing `copy_to_tempfile` method on "uploader" task
* DEV: Refactor a bit more
Deduplicate and move most of threading premitives to base task as-is
* DEV: Remove redundant condition in uploads db migration
* DEV: More deduplication
Move task retry logic to base class and tidy up other implementation
details carried over from the existing script
* Updates GitHub Actions
* Switches from `bundler/inline` to an optional group in the `Gemfile` because the previous solution didn't work well with rspec
* Adds the converter framework and tests
* Allows loading private converters (see README)
* Switches from multiple CLI tools to a single CLI
* Makes DB connections reusable and adds a new abstraction for the `IntermediateDB`
* `IntermediateDB` acts as an interface for IPC calls when a converter steps runs in parallel (forks). Only the main process writes to the DB.
* Includes a simple example implementation of a converter for now.
