I would like to bind a component property value to the URL of my iron-ajax component.

My scenario looks like this...

I have an 'iron-meta' component which I use to store all of my API endpoints like so...

<iron-meta id="services" key="services" value=
    '{
            "baseApiUrl": {
              "foo":"/api/{dynamic_id}",
              "bar":"/api/{dynamic_id}/stuff"
            }
      }'>
</iron-meta>

I then import this meta object into the custom component that requires this endpoint for an iron-ajax and bind the value of this meta object to a "services" property in my custom component, like so...

<iron-meta-query id="query" key="services" value="{{services}}"></iron-meta-query>

For me to use a "services" endpoint that requires a component property value currently I need to access the iron-ajax by id and do a string replace on the API string to replace it with my component property value, like so...

_computeUrl: function(services,dynamic_id) {
    return this.services.baseApiUrl.bar.replace("{dynamic_id}", dynamic_id);
  }

I would like to directly bind my custom components' "dynamic_id" property to the imported "[[services.baseApiUrl.bar]]" value so that the below sample...

<iron-meta-query id="query" key="services" value="{{services}}"></iron-meta-query>

    <iron-ajax id="getHomeData"
        auto
        handle-as="json"
        content-type="application/json"
        url$="[[services.baseApiUrl.bar]]"
        method="GET"
        last-response="{{_response}}">
    </iron-ajax>

//dynamic_id = 1234;

...would resolve the iron-ajax URL to look like this...

"/api/1234/stuff"

without having to do any string replace on the imported service URL.

My question is, is there a polymer way to do this, if so, how can I do this?