addRelay method
Add a relay to the pool.
Implementation
void addRelay(String relayUrl) {
_relayHealth[relayUrl] = RelayHealthStatus(
url: relayUrl,
isHealthy: true,
lastCheckedAt: DateTime.now(),
);
_activeConnections[relayUrl] = 0;
_failureCount[relayUrl] = 0;
logger.log('Relay $relayUrl added to pool');
}