Replace JSONResponse with Response to fix runtime error #628

[joelvdavies]

Description

See #628. It seems JSONResponse doesn really allow for returning None with a 204 (fastapi/fastapi#4939 (comment)), so switching to use a standard response instead.

Testing instructions

Add a set up instructions describing how the reviewer should test the code

• Review code
• Check Actions build
• Review changes to test coverage

Agile board tracking

Closes #628

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.32%. Comparing base (59b88ea) to head (8a0333c).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #629   +/-   ##
========================================
  Coverage    97.32%   97.32%           
========================================
  Files           57       57           
  Lines         1983     1983           
========================================
  Hits          1930     1930           
  Misses          53       53           

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