DOCS: update docstrings on several modules

[lwasser]

This is a small PR to wrap up the items in #445 which won't get merged given the restructure. captured all docstring updates here. there is some more work to be done on docstrings throughout abc-classroom ... addresses in part #463

[codecov]

Codecov Report

Merging #464 (21e481e) into main (9f3f7f7) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #464   +/-   ##
=======================================
  Coverage   60.46%   60.46%           
=======================================
  Files          20       20           
  Lines        1171     1171           
=======================================
  Hits          708      708           
  Misses        463      463           

Flag	Coverage Δ
unittests	60.46% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
abcclassroom/auth.py	13.88% <ø> (ø)
abcclassroom/git.py	45.28% <ø> (ø)
abcclassroom/github.py	18.75% <ø> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9f3f7f7...21e481e. Read the comment docs.

[lwasser]

merging this as it is only docstring updates!