Datasource with and through


I am trying to build a datasource that will filter by both the User’s facility selection and the User’s id. I have:

   dataSource ManageAlertSubscriptionsData {
      "collection": true,
      "c3type": "ApplicationAlertEngine",
      "c3function": "getAlertSubscriptionPreferences",
      "responseSelector": "objs",
      "c3arguments": {
         "spec": {
            "filter": " == '{{ }} && == {{ <what goes here??> }}'",
            "include": ",,, subscribed"

Is there some way to pass the user ID through? I am a little unfamiliar with params. How can I check what the page params would be at that point or potentially add the user Id to them?

#2 I believe