tests: add logged_user context manager

[bouttier]

Usage:

with logged_user(client, user):
    response = client.get(url)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (83f4710) 51.72% compared to head (2adb676) 51.47%.

❗ Current head 2adb676 differs from pull request most recent head 63f5b86. Consider uploading reports for the commit 63f5b86 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           develop      #84      +/-   ##
===========================================
- Coverage    51.72%   51.47%   -0.26%     
===========================================
  Files           14       14              
  Lines          725      713      -12     
===========================================
- Hits           375      367       -8     
+ Misses         350      346       -4     

Flag	Coverage Δ
pytest	51.47% <ø> (-0.26%)	⬇️

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