Add tests for timezone-aware datetimes

[kmshin1397]

Add tests to accompany my PR on baselayer: cesium-ml/baselayer#187

The baselayer diffs on this PR should be equivalent to pinning to latest baselayer and then adding the changes in that PR on top.

[pep8speaks]

Hello @kmshin1397! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file template_app/tests/models/test_timezone_datetimes.py:

Line 50:80: E501 line too long (85 > 79 characters)

Comment last updated at 2021-05-03 20:25:01 UTC

[kmshin1397]

Probably easiest if #100 goes in first

[acrellin]

Looks good. Perhaps also check that when fetching the new user, the created_at column is what is expected?

[kmshin1397]

Hmm not sure why the newly-merged GA workflow isn't running. Maybe it's only triggered for new PRs and new commits to PRs existing before the GA was implemented

[kmshin1397]

Also not sure what the best practice is here: these tests will technically fail without the changes in cesium-ml/baselayer#187, but this is also designed to test the logic in there. I could commit those baselayer changes here as well (which is what I did when I first made this PR) but that involves pinning the baselayer submodule to a dangling commit and then we'd have to re-pin to the correct commit once the baselayer PR is merged, which also seems bad. For now, just leaving this as is.