refactor: Divide file save function into 2 parts, add UTs

[o-kopysov]

Pull Request

Description

The file-saving function is divided into 2 parts for better maintenance.
Added unit tests to cover more branches.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Code cleanup/refactoring
• Documentation update
• This change requires a documentation update
• CI system update
• Test Coverage update

Testing

Local run of UTs.

Checklist:

• My code follows the style guidelines of this project
• My code meets the required code coverage for lines (90% and above)
• My code meets the required code coverage for branches (80% and above)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 87.75510% with 6 lines in your changes missing coverage. Please review.

Project coverage is 93.89%. Comparing base (26d4ae7) to head (70f7be9).

Files with missing lines	Patch %	Lines
src/main/java/com/lpvs/util/LPVSFileUtil.java	86.66%	3 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #641      +/-   ##
============================================
+ Coverage     93.63%   93.89%   +0.25%     
- Complexity      635      640       +5     
============================================
  Files            52       52              
  Lines          2185     2195      +10     
  Branches        255      254       -1     
============================================
+ Hits           2046     2061      +15     
+ Misses           62       58       -4     
+ Partials         77       76       -1     

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[t-naumenko]

LGTM

[o-konoval]

LGTM

[m-rudyk]

I have no objections, approved.