feat(TER-338): Add Social Security Number pattern detection to FormatConstraint

[ericpsimon]

Summary

This PR implements Social Security Number (SSN) pattern detection for the FormatConstraint in Term, providing Deequ-compatible containsSocialSecurityNumber() functionality.

Changes

🎯 New SSN Detection Feature

• FormatType::SocialSecurityNumber: New format type variant for SSN validation
• Pattern Matching: Supports both hyphenated (XXX-XX-XXXX) and non-hyphenated (XXXXXXXXX) formats
• Invalid SSN Exclusion: Automatically excludes known invalid SSNs:
  • Numbers starting with 000, 666, or 9xx
  • Middle digits of 00
  • Last four digits of 0000
• Threshold-based Validation: Configurable threshold for percentage of valid SSNs required

🔧 API Additions

• FormatConstraint::social_security_number() - Direct builder method for SSN validation
• CheckBuilder::contains_ssn() - Convenience method on Check builder for easy SSN validation
• Full integration with existing FormatConstraint infrastructure

✅ Comprehensive Testing

• Valid SSN format testing (hyphenated and non-hyphenated)
• Invalid pattern rejection testing
• Mixed data validation with proper null handling
• Threshold-based validation tests
• Edge case coverage including historically used example SSNs

Test Plan

• Test valid SSN formats (XXX-XX-XXXX and XXXXXXXXX)
• Verify invalid SSN patterns are rejected (000-xx-xxxx, xxx-00-xxxx, 666-xx-xxxx, 9xx-xx-xxxx)
• Test threshold-based validation behavior
• Verify null value handling with FormatOptions
• Test edge cases and mixed data scenarios
• All tests passing with cargo test test_ssn

Related

• Linear Ticket: TER-338
• Implements Deequ-compatible SSN detection for data validation

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