Allow ReferentialIntegrity metric to work on composite keys

[pvk-developer]

Resolves #838
CU-86b8atdg7

[sdv-team]

Task linked: CU-86b8atdg7 SDMetrics - Allow the ReferentialIntegrity metric to work with composite keys #838

[sarahmish]

Maybe add a test for compute_breakdown with composite keys that have null values? This should include when the entire both keys are null and one only a single key is null in the composite key

[sarahmish]

what if INDICATOR_NAME is part of existing columns? Maybe you can create a temporary indicator using _create_unique_name?

indicator = _create_unique_name(
    INDICATOR_NAME, pk_columns + fk_columns
)

[sarahmish]

@pvk-developer I was referring to an already existing function in sdv._utils, similar to how it's being used here.

[pvk-developer]

Done in 64166c9

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.73%. Comparing base (c3ed586) to head (6ff71f7).
⚠️ Report is 5 commits behind head on feature/composite-keys.

Additional details and impacted files

@@                    Coverage Diff                     @@
##           feature/composite-keys     #859      +/-   ##
==========================================================
+ Coverage                   95.72%   95.73%   +0.01%     
==========================================================
  Files                         117      117              
  Lines                        4914     4927      +13     
==========================================================
+ Hits                         4704     4717      +13     
  Misses                        210      210              

Flag	Coverage Δ
integration	80.84% <33.33%> (-0.14%)	⬇️
unit	84.45% <100.00%> (+0.04%)	⬆️

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[sarahmish]

Left one comment to make the condition easier to read, but this is ready for merge