chore: add middleware to transform error and rename placeholder.txt

[ShiningRush]

• Add middleware to transform error, resolve [refactor][bug] bind params to struct error should response error with 400 status  #568
• Rename placeholder.txt to .gitkeep, It is more suitable

[codecov-io]

Codecov Report

Merging #899 (4766942) into master (277ae59) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #899   +/-   ##
=======================================
  Coverage   43.03%   43.03%           
=======================================
  Files          18       18           
  Lines        1271     1271           
=======================================
  Hits          547      547           
  Misses        632      632           
  Partials       92       92           

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[juzhiyuan]

.gitkeep looks good to me

[idbeta]

@ShiningRush I found that you only added test cases to the routed (uri). should we add test cases in these situations? #568 (comment)

[idbeta]

@ShiningRush I found that you only added test cases to the routed (uri). should we add test cases in these situations? #568 (comment)

I have tested the problematic scenes, and there are indeed no problems.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 43.03%. Comparing base (277ae59) to head (4766942).
Report is 825 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #899   +/-   ##
=======================================
  Coverage   43.03%   43.03%           
=======================================
  Files          18       18           
  Lines        1271     1271           
=======================================
  Hits          547      547           
  Misses        632      632           
  Partials       92       92           

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