Add pytest setup fixture to ensure .env file exists

[annshress]

… with appropriate variables

Addresses https://github.com/niaid/image_portal_workflows/issues/287

Changes

• Removes monkeypatching config in pytest
• Mandates .env files (checked only during pytest)

This PR doesn't introduce any:

• [x] Binary files
• [x] Temporary files, auto-generated files
• [x] Secret keys
• [x] Local debugging print statements
• [x] Unwanted comments (e.g: # Gets user from environment for code os.environ['user'] )

This PR contains valid:

• [x] tests

[github-actions[bot]]

Coverage report

The coverage rate went from 67.12% to 26.89% :arrow_down: The branch rate is 13%.

None of the new lines are part of the tested code. Therefore, there is no coverage data about them.