fix: publishEvent method to support text content types and improve serialization handling

[matheusandre1]

Description

Fixes content-type mismatch in publishEvent: when a text content type (text/* or application/xml) is set and the default serializer is used, String/Number/Boolean data is now sent as raw text instead of being JSON-quoted. This matches the behavior already used by publishEvents (bulk) via DefaultContentTypeConverter.

Behavior change

"hello" published with text/plain is now sent as hello instead of "hello". Subscribers that strip the extra quotes should remove that workaround. Publishing without a content type is unchanged (application/json), as are custom serializers and non-text content types.

Issue reference

We strive to have all PR being opened based on an issue, where the problem or feature have been discussed prior to implementation.

Fixes: #779

RELEASE NOTE: FIX publishEvent no longer JSON-quotes String/Number/Boolean payloads when a text content type is set

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Extended the documentation

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.74%. Comparing base (77f6794) to head (cadcf52).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1831      +/-   ##
============================================
+ Coverage     79.66%   79.74%   +0.07%     
- Complexity     2683     2689       +6     
============================================
  Files           267      267              
  Lines          7923     7928       +5     
  Branches        839      841       +2     
============================================
+ Hits           6312     6322      +10     
+ Misses         1252     1249       -3     
+ Partials        359      357       -2     

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