[LiftController] Add ProducesResponseType attributes

[imnasnainaec]

Also, make NotFound objects more explicit.

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This change is 

[codecov]

Codecov Report

Attention: Patch coverage is 60.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 73.69%. Comparing base (0881512) to head (9f57cf9).

Files with missing lines	Patch %	Lines
Backend/Controllers/LiftController.cs	60.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3849      +/-   ##
==========================================
- Coverage   73.69%   73.69%   -0.01%     
==========================================
  Files         287      287              
  Lines       10773    10772       -1     
  Branches     1344     1344              
==========================================
- Hits         7939     7938       -1     
  Misses       2437     2437              
  Partials      397      397              

Flag	Coverage Δ
backend	83.52% <60.00%> (-0.01%)	⬇️
frontend	66.03% <ø> (ø)

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[jasonleenaylor]

Reviewed 1 of 1 files at r1, 1 of 1 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @imnasnainaec)