feat: add migrations check

[nsprenkle]

About

Adds a migrations check, mirrored after similar workflows in edx-platform, edx-notes-api, and edx-analytics-dashboard, to name a few.

Migration check further modified (based on this test) to actually fail when there are missing migration files.

JIRA: https://2u-internal.atlassian.net/browse/AU-820

Testing Instructions

• Verify new step (Migrations check on mysql8) appears on PRs. Should fail if a migration fails or is missing for future PRs.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (0962818) 93.43% compared to head (900111a) 93.43%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #196   +/-   ##
=======================================
  Coverage   93.43%   93.43%           
=======================================
  Files          18       18           
  Lines        1996     1996           
  Branches      125      125           
=======================================
  Hits         1865     1865           
  Misses        118      118           
  Partials       13       13           

Flag	Coverage Δ
unittests	93.43% <100.00%> (ø)

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

Impacted Files	Coverage Δ
submissions/__init__.py	100.00% <100.00%> (ø)

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[jansenk]

I think that the check should be failing on this PR I made off of your branch: https://github.com/openedx/edx-submissions/pull/197/files

[jansenk]

Wow, it looks like those aren't actually doing that check, it's just a unit test that's running?

openedx/edx-platform#32301

check migrations and check migrations mysql8 both pass! it's a unit test that fails, specifically this one.

[nsprenkle]

Wow, it looks like those aren't actually doing that check, it's just a unit test that's running?

openedx/edx-platform#32301

check migrations and check migrations mysql8 both pass! it's a unit test that fails, specifically this one.

@jansenk, is that to say we should be doing that as a unit test, as in edx-platform? I'm happy to do it that way instead, but am just making educated guesses at this time.

[jansenk]

the test fails on my test branch! looks great
https://github.com/openedx/edx-submissions/actions/runs/5083648614/jobs/9134917710?pr=197