feat: Create staff fixture

[zachaysan]

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Changes

Add a new fixture to transition to testing more routes by default at a lower level of access to ensure staff members are:

1. Able to do stuff they're supposed to do.
2. Not able to do stuff they're not supposed to do.

Essentially, start by default by using the staff fixture since the resulting tests are more robust since admin users are automatically able to sail through most permissions classes.

How did you test this code?

By using the same code in this PR

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Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (6e6a48b) 95.63% compared to head (5ad077f) 95.62%.
Report is 6 commits behind head on main.

❗ Current head 5ad077f differs from pull request most recent head c6d00ec. Consider uploading reports for the commit c6d00ec to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2928      +/-   ##
==========================================
- Coverage   95.63%   95.62%   -0.01%     
==========================================
  Files        1011     1011              
  Lines       29006    29015       +9     
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+ Hits        27741    27747       +6     
- Misses       1265     1268       +3     

Files	Coverage Δ
api/conftest.py	97.60% <70.00%> (-1.16%)	⬇️

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[khvn26]

Looks good, two concerns though:

1. I'd think on the naming some more since, AFAIK, we don't use the word "staff" anywhere. user_user is awkward of course, maybe user_role_user is better.
2. I'm reluctant to merge this without any tests actually using the fixture to avoid adding dead code.

[zachaysan]

1. I'd think on the naming some more since, AFAIK, we don't use the word "staff" anywhere. user_user is awkward of course, maybe user_role_user is better.

I bounced it off Matt and he's with me on staff being a sorta concise, readable word. I think it's better than the alternatives.

2. I'm reluctant to merge this without any tests actually using the fixture to avoid adding dead code.

I already have some tests that use this fixture. They're just in PRs that may be around for a while and I want this new fixture to use now. Plus we should all be defaulting to using this fixture anyway, since the admin client side steps many of the permissions checks.