Increase test coverage to 100% for api directory

[jrobbins]

Describe the bug You can run a test coverage report by doing npm run coverage then npm run view-coverage and browsing localhost:8080.

Our unit test coverage for the /api directory is pretty good, but there are a few gaps:

• [x] channels_api.py
• [x] converters.py
• [x] stages_api.py
• [ ] A few untested lines in the other files

Ideally untested code would become tested code by adding new unit tests. However, if needed we can mark specific lines as excluded from the coverage metrics. https://coverage.readthedocs.io/en/stable/excluding.html

[KyleJu]

Converters.py has been improved to 98%

[KyleJu]

With #2836, all API files have achieved at least 90% test coverage