External services like smtp.gmail.com and xmpp.earth can be unreliable
in CI environments. Added retry logic (up to 3 attempts) to prevent
false test failures due to network issues.
- Replace client.badssl.com tests with unit tests for parseTlsAlertNumber and getTlsAlertName
- Export helper functions for testing
- Keep one integration test for connection success scenario
- Test rejection when expecting TLS alert but connection succeeds
- Test UP status when expected TLS alert is received
- Test rejection when different TLS alert is received than expected