Added the prometheus_server_lts for nginx proxy cfg

For prometheus server LTS instance we should have a nginx
proxy config to be able to access its UI.

Change-Id: I30402cd80555afda62afe17d57b94f4616710e2e
Related-Bug: PROD-26822
diff --git a/nginx/server/proxy/monitoring/prometheus_server_lts.yml b/nginx/server/proxy/monitoring/prometheus_server_lts.yml
new file mode 100644
index 0000000..512d018
--- /dev/null
+++ b/nginx/server/proxy/monitoring/prometheus_server_lts.yml
@@ -0,0 +1,18 @@
+parameters:
+  nginx:
+    server:
+      enabled: true
+      site:
+        nginx_proxy_prometheus_server_lts:
+          enabled: true
+          type: nginx_proxy
+          name: prometheus_server_lts
+          proxy:
+            host: ${_param:stacklight_telemetry_address}
+            port: 9090
+            protocol: http
+          host:
+            name: ${_param:cluster_public_host}
+            port: 9090
+            protocol: https
+          ssl: ${_param:nginx_proxy_ssl}