fix: harden websocket heartbeat under load

docker/tinode/config.template

@@ -5,6 +5,8 @@
 	"static_mount": "/",
 	"grpc_listen": ":16060",
 	"grpc_keepalive_enabled": true,
+	"ws_ping_period_seconds": $WS_PING_PERIOD_SECONDS,
+	"ws_pong_wait_seconds": $WS_PONG_WAIT_SECONDS,
 	"api_key_salt": "$API_KEY_SALT",
 	"max_message_size": 4194304,
 	"max_subscriber_count": 128,

docker/tinode/entrypoint.sh

@@ -13,6 +13,8 @@ else
 	CONFIG=working.config
 
 	: "${REDIS_KEY_PREFIX:=im}"
+	: "${WS_PING_PERIOD_SECONDS:=15}"
+	: "${WS_PONG_WAIT_SECONDS:=90}"
 	: "${CLUSTER_PROXY_TO_MASTER_BUFFER:=4096}"
 	: "${CLUSTER_PROXY_TO_MASTER_WORKERS:=16}"
 	: "${CLUSTER_PROXY_TO_MASTER_ENQUEUE_TIMEOUT_MS:=300}"