updated union table operations and added it to merge operations

[Ishankoradia]

No description provided.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 90.90909% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 72.64%. Comparing base (663b829) to head (dd9b568).

Files	Patch %	Lines
dbt_automation/operations/mergeoperations.py	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #94      +/-   ##
==========================================
- Coverage   72.65%   72.64%   -0.01%     
==========================================
  Files          28       28              
  Lines        1309     1316       +7     
==========================================
+ Hits          951      956       +5     
- Misses        358      360       +2     

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