[ISSUE #4286] Fix response body is not recognised as JSON in query WebHook config endpoints

[Pil0tXia]

Fixes #4286.

Motivation

The response body is not recognised as JSON in Postman, and the Content-Type header missing:

Modifications

That's because NetUtils.sendSuccessResponseHeaders(httpExchange); is in front of httpExchange.getResponseHeaders().add(CONTENT_TYPE, APPLICATION_JSON); and headers are sent out before they are set correctly.

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)
• If a feature is not applicable for documentation, explain why?
• If a feature is not documented yet in this PR, please create a followup issue for adding the documentation

[codecov]

Codecov Report

Merging #4287 (5ebe5ee) into master (c18ef05) will increase coverage by 0.00%.
Report is 1 commits behind head on master.
The diff coverage is 0.00%.

❗ Current head 5ebe5ee differs from pull request most recent head 93f225d. Consider uploading reports for the commit 93f225d to get more accurate results

@@            Coverage Diff            @@
##             master    #4287   +/-   ##
=========================================
  Coverage     16.87%   16.87%           
- Complexity     1426     1427    +1     
=========================================
  Files           593      593           
  Lines         26068    26068           
  Branches       2396     2396           
=========================================
+ Hits           4398     4400    +2     
+ Misses        21229    21228    -1     
+ Partials        441      440    -1     

Files Changed	Coverage Δ
...e/admin/handler/QueryWebHookConfigByIdHandler.java	26.66% <0.00%> (ø)
...ndler/QueryWebHookConfigByManufacturerHandler.java	28.57% <0.00%> (ø)

... and 1 file with indirect coverage changes

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