Create ETL task to map columns

[Yun-Wu]

• Add a column mapping task
• Add the task to registry
• Add unittest

#34

[cisaacstern]

I know you didn't ask for review yet, but just wanted to say this is looking awesome so far!!

Installing pre-commit and running pre-commit run --all-files should resolve the linting issues 🙏

[Yun-Wu]

@cisaacstern thanks for the prompt review haha! Can you take a look again?

[cisaacstern]

LGTM!

Commented on a few small nits.

The only thing from the linked issue I don't see explicitly covered here is:

"The function should provide a warning when critical columns (e.g., 'geometry') are being dropped."

Not sure if you'd like to address that now or in a follow-on. Approving this to indicate that either is fine for me.

In general, I really like the pattern of a full module of tests in for a single task and all its edge cases, that focuses on the behavior of the function in "pure python" mode (without any of the distributed behaviors interfering with the clarity of the logic). I think we should adopt this pattern for all of the task testing. The testing I have for the existing tasks is too opaque!

[cisaacstern]

Awesome, thanks Yun!!

One last typo noted below. Otherwise, if you're happy here, I'm good to merge!