FIX: Improved error message in the case of SQL constraint violation on foreign keys

[Agnul97]

Brief description of the PR.
I wanted to return a more specific error message that notifies clients that they are trying to break a fk constraints, to let them know precisely what they are doing wrong. Currently, in such cases, a too general 500 internal persistence error is returned

Description of the solution adopted
With these changes, a 409 error is returned instead, with a message that notifies precisely a fk violation if it's detected. Otherwise, a more general error message is returned if other SQL constraint violations are present

[codecov]

Codecov Report

Attention: Patch coverage is 38.88889% with 11 lines in your changes missing coverage. Please review.

Project coverage is 16.71%. Comparing base (4e2973c) to head (4ee9ece).
Report is 4 commits behind head on develop.

Files with missing lines	Patch %	Lines
...QLIntegrityConstraintViolationExceptionMapper.java	0.00%	9 Missing ⚠️
...KapuaSQLIntegrityConstraintViolationException.java	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #4167   +/-   ##
==========================================
  Coverage      16.71%   16.71%           
  Complexity        22       22           
==========================================
  Files           2039     2041    +2     
  Lines          53018    53036   +18     
  Branches        4453     4455    +2     
==========================================
+ Hits            8860     8867    +7     
- Misses         43755    43766   +11     
  Partials         403      403           

Files with missing lines	Coverage Δ
...clipse/kapua/commons/util/KapuaExceptionUtils.java	97.50% <100.00%> (+0.27%)	⬆️
...c/main/java/org/eclipse/kapua/KapuaErrorCodes.java	100.00% <100.00%> (ø)
...KapuaSQLIntegrityConstraintViolationException.java	50.00% <50.00%> (ø)
...QLIntegrityConstraintViolationExceptionMapper.java	0.00% <0.00%> (ø)