Feat/is null

[reifocS]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/sipios/spring-search//blob/main/CONTRIBUTING.md##Commit-messages
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

User can not search for null values
Issue Number: 52

What is the new behavior?

User can filter on null /not null values

Does this PR introduce a breaking change?

• Yes
• No

Other information

[codecov]

Codecov Report

Attention: Patch coverage is 74.07407% with 7 lines in your changes missing coverage. Please review.

Project coverage is 83.23%. Comparing base (912614d) to head (131c7ab).
Report is 2 commits behind head on master.

❗ Current head 131c7ab differs from pull request most recent head 8355580

Please upload reports for the commit 8355580 to get more accurate results.

Files	Patch %	Lines
.../sipios/springsearch/strategies/BooleanStrategy.kt	0.00%	0 Missing and 1 partial ⚠️
...com/sipios/springsearch/strategies/DateStrategy.kt	0.00%	0 Missing and 1 partial ⚠️
...m/sipios/springsearch/strategies/DoubleStrategy.kt	0.00%	0 Missing and 1 partial ⚠️
...sipios/springsearch/strategies/DurationStrategy.kt	0.00%	0 Missing and 1 partial ⚠️
.../sipios/springsearch/strategies/InstantStrategy.kt	0.00%	0 Missing and 1 partial ⚠️
.../com/sipios/springsearch/strategies/IntStrategy.kt	0.00%	0 Missing and 1 partial ⚠️
...ipios/springsearch/strategies/LocalTimeStrategy.kt	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master      #82      +/-   ##
============================================
+ Coverage     83.00%   83.23%   +0.22%     
- Complexity      123      132       +9     
============================================
  Files            22       22              
  Lines           306      328      +22     
  Branches         43       49       +6     
============================================
+ Hits            254      273      +19     
+ Misses           28       26       -2     
- Partials         24       29       +5     

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[github-actions]

⚡ Coverage report

Overall Project	85.54% -0.28%	🍏
Files changed	95.4%	🍏

File	Coverage
EnumStrategy.kt	100%	🍏
LocalDateStrategy.kt	97.25%	🍏
QueryVisitorImpl.kt	96.93%	🍏
IntStrategy.kt	95.61%	🍏
SearchOperation.kt	94.63%	🍏
DateStrategy.kt	87.07%	🍏
LocalDateTimeStrategy.kt	86.24%	🍏
LocalTimeStrategy.kt	84.4% -1.83%	❌
ParsingStrategy.kt	82.83%	🍏
CollectionStrategy.kt	82.61%	🍏
UUIDStrategy.kt	66.67%	🍏
BooleanStrategy.kt	66.67%	🍏
InstantStrategy.kt	66.06% -1.83%	❌
FloatStrategy.kt	62.28%	🍏
DurationStrategy.kt	60.55% -1.83%	❌
DoubleStrategy.kt	60.53% -1.75%	❌