## Description
Allow users to download a completed document via API.
## Testing Performed
Tested the code locally by trying to download both draft and completed
docs. Works as expected.
## Checklist
- [x] I have tested these changes locally and they work as expected.
- [ ] I have added/updated tests that prove the effectiveness of these
changes.
- [ ] I have updated the documentation to reflect these changes, if
applicable.
- [x] I have followed the project's coding style guidelines.
- [ ] I have addressed the code review feedback from the previous
submission, if applicable.
<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit
- **New Features**
- Implemented functionality to download signed documents directly from
the app.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Extracts the API implementation to a package so we can
potentially reuse it across different applications in the
event that we move off using a Next.js API route.
Additionally tidies up the tokens page and form to be more simplified.
