fix: prepare native cluster deployment

docker/tinode/config.template

@@ -271,11 +271,7 @@
 
 	"cluster_config": {
 		"self": "",
-		"nodes": [
-			{"name": "tinode-0", "addr": "tinode-0:12000"},
-			{"name": "tinode-1", "addr": "tinode-1:12001"},
-			{"name": "tinode-2", "addr": "tinode-2:12002"}
-		],
+		"nodes": $CLUSTER_NODES_JSON,
 		"failover": {
 			"enabled": true,
 			"heartbeat": 100,

docker/tinode/entrypoint.sh

@@ -13,6 +13,9 @@ else
 	CONFIG=working.config
 
 	: "${REDIS_KEY_PREFIX:=im}"
+	if [ -z "$CLUSTER_NODES_JSON" ] ; then
+		CLUSTER_NODES_JSON='[{"name":"tinode-0","addr":"tinode-0:12000"},{"name":"tinode-1","addr":"tinode-1:12001"},{"name":"tinode-2","addr":"tinode-2:12002"}]'
+	fi
 
 	# Remove the old config.
 	rm -f working.config