feat: add Associated Persons (AP) domain support

[ankonyeni]

Summary

Adds Associated Persons (AP) domain support to combine_supp and build_qnam

Changes

combine_supp

• Detects whether the supp dataset uses APID or USUBJID and resolves id_var dynamically
• Errors if both APID and USUBJID are present in the supp dataset
• Errors if neither APID nor USUBJID are present in the supp dataset
• Errors if both APID and USUBJID are present in the parent dataset
• Validates that STUDYID, DOMAIN, and the resolved id_var are present in the parent dataset

combine_supp_join

• Updated by key resolution to include APID alongside USUBJID

build_qnam

• Detects whether the dataset uses APID or USUBJID and resolves id_var dynamically
• Errors if both APID and USUBJID are present in the dataset
• Errors if neither APID nor USUBJID are present in the dataset
• Updated select, distinct, and output column to use resolved id_var
• Updated ambiguity error message to reference the resolved id_var

Tests

New tests added for both combine_supp and build_qnam covering:

• Happy path for both USUBJID and APID domains
• Error cases for both/neither ID column scenarios
• Required parent column validation
• IDVAR column existence validation
• Correct output structure, column names, and values for AP domains
• Blank and NA IDVAR handling for subject-level records
• Ambiguity error message referencing the correct ID column
• Multiple subjects in AP datasets

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.99%. Comparing base (111fd3b) to head (3dd4a95).
⚠️ Report is 104 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #133      +/-   ##
==========================================
+ Coverage   82.19%   83.99%   +1.79%     
==========================================
  Files           7        7              
  Lines         691      831     +140     
==========================================
+ Hits          568      698     +130     
- Misses        123      133      +10     

Files with missing lines	Coverage Δ
R/supp.R	79.16% <100.00%> (+8.44%)	⬆️

... and 3 files with indirect coverage changes

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