OP#188 add option to allow external remote write in gerenal

templates/prometheus.yml.erb

@@ -35,4 +35,11 @@ remote_write:
   - url: "http://localhost:9090/api/v1/write"
     basic_auth:
       username: <%= @ps_auth_user %>
-      password: <%= @ps_auth_pass %>
+      password: <%= @ps_auth_pass %>
+<% if @ps_write_external == true -%>
+remote_write:
+  - url: "<%= @ps_external_url %>"
+    basic_auth:
+      username: <%= @ps_auth_ext_user %>
+      password: <%= @ps_auth_ext_pass %>
+<% end -%>