feat: add concat or null operator

[aaron-steinfeld]

Description

This new operator, CONCAT_OR_NULL adds a variant of concat behavior where concat'ing null with another value returns null. Our current CONCAT operator returns the value in this case (would rather flip this behavior and have the null propagate by default, but that's breaking). Similar behavior variants are present in SQL databases such as https://docs.microsoft.com/en-us/sql/t-sql/statements/set-concat-null-yields-null-transact-sql?view=sql-server-ver15#:~:text=When%20SET%20CONCAT_NULL_YIELDS_NULL%20is%20ON,treated%20as%20an%20empty%20string).

Testing

Added UT, verified E2E

Checklist:

• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• Any dependent changes have been merged and published in downstream modules

[codecov]

Codecov Report

Merging #93 (547bb82) into main (aceb6fd) will increase coverage by 0.04%.
The diff coverage is 85.71%.

@@             Coverage Diff              @@
##               main      #93      +/-   ##
============================================
+ Coverage     80.71%   80.76%   +0.04%     
- Complexity      222      225       +3     
============================================
  Files            27       28       +1     
  Lines           752      759       +7     
  Branches         56       56              
============================================
+ Hits            607      613       +6     
- Misses           98       99       +1     
  Partials         47       47              

Flag	Coverage Δ	Complexity Δ
integration	80.76% <85.71%> (+0.04%)	147.00 <3.00> (+3.00)
unit	67.95% <85.71%> (+0.17%)	206.00 <3.00> (+3.00)

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Impacted Files	Coverage Δ	Complexity Δ
...ervice/projection/functions/ConcatenateOrNull.java	75.00% <75.00%> (ø)	3.00 <3.00> (?)
...ervice/projection/AttributeProjectionRegistry.java	100.00% <100.00%> (ø)	3.00 <0.00> (ø)

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[github-actions]

Unit Test Results

21 files  +1  21 suites  +1   11s ⏱️ ±0s
77 tests +2  77 ✔️ +2  0 💤 ±0  0 ❌ ±0 

Results for commit bc6b0f3. ± Comparison against base commit aceb6fd.