Add comprehensive edge case tests for NoSQL operator detection

[Copilot]

Addresses missing test coverage for boundary conditions in NoSQL injection detection logic, specifically around dollar sign parsing and operator identification.

Changes

• Edge cases for dollar signs: Tests for $ at string end ("price$"), followed by non-alphabetic chars ("$123", "$_id"), and with unknown operators ("$unknown")

• Boundary delimiter coverage: Tests for operators after all delimiters from isNoSQLOperatorBoundary ({, [, ,, :, ", ', (), plus whitespace variants (space, tab, newline)

• False positive prevention: Tests ensuring mid-word operators ("test$nevalue") and legitimate dollar usage don't trigger detection

Added 24 test cases in TestNoSQLInjectionDetectorEdgeCases using table-driven approach for clarity and maintainability.

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[Copilot]

Pull request overview

This PR enhances test coverage for NoSQL injection detection by adding comprehensive edge case tests that verify correct behavior for boundary conditions in dollar sign parsing and operator identification.

Changes:

• Restructured TestNoSQLInjectionDetectorEdgeCases with improved naming (shouldErr instead of wantError)
• Added 25 test cases covering dollar signs at string end, non-alphabetic followers, unknown operators, all boundary delimiters, and false positive scenarios
• Simplified test assertion logic for better readability

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