Job service: minor fixes/updates

[peteski22]

What's changing

• Fix fstring for log entry
• update docstring
• rename s3 fs vars

If this PR is related to an issue or closes one, please link it here.

How to test it

Steps to test the changes:

Additional notes for reviewers

Anything you'd like to add to help the reviewer understand the changes you're proposing.

I already...

• Tested the changes in a working environment to ensure they work as expected
• Added some tests for any new functionality
• Updated the documentation (both comments in code and product documentation under /docs)
• Checked if a (backend) DB migration step was required and included it if required

[njbrake]

LGTM