Kristjan ESPERANTO 2b55b8e0f4 refactor(clientonly): modernize code structure and add comprehensive tests (#4022) ...

This PR improves `clientonly` start option with better code structure,
validation, and comprehensive test coverage.

### Changes

**Refactoring:**
- Improved parameter handling with explicit function parameter passing
instead of closure
- Added port validation (1-65535) with proper NaN handling
- Removed unnecessary IIFE wrapper (Node.js modules are already scoped)
- Extracted `getCommandLineParameter` as a reusable top-level function
- Enhanced error reporting with better error messages
- Added connection logging for debugging

**Testing:**
- Added comprehensive e2e tests for parameter validation
- Test coverage for missing/incomplete parameters
- Test coverage for local address rejection (localhost, 127.0.0.1, ::1,
::ffff:127.0.0.1)
- Test coverage for port validation (invalid ranges, non-numeric values)
- Test coverage for TLS flag parsing
- Integration test with running server

### Testing

All tests pass:
```bash
npm test -- tests/e2e/clientonly_spec.js
# ✓ 18 tests passed

2026-01-28 20:48:47 +01:00

..

index.js

refactor(clientonly): modernize code structure and add comprehensive tests (#4022)

2026-01-28 20:48:47 +01:00