Add application tests

[matthewfeickert]

Please provide us with the following information:

This issue is for a: (mark with an x)

- [ ] bug report -> please search issues before submitting
- [x] feature request
- [ ] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)

It would be good to add pytest based tests for the applicaiton functionality. This will require some mock data similar in form to what is expected in

assign-reviews/assign_reviews.py

Lines 20 to 21 in 084be95

	df_submissions = pd.read_csv("2023_submissions_to_assign.csv")
	df_reviewers = pd.read_csv("2023_reviewers_to_assign.csv")

Then unit and application tests can be written that in addition to typical use target edge cases that have been encournted in the past.