Dynamic sourceField, destField in ES query

[curran]

Currently, the custom middleware that queries ES when clicking on chord ribbons has hard-coded values for the source and destination fields.

          var options = {
            index: index,
            body: {
              query: {
                bool: {
                  must: [
                    {
                      "term": {
                        "nuage_metadata.sourcepolicygroups": d.source
                      }
                    },
                    {
                      "term": {
                        "nuage_metadata.destinationpolicygroups": d.destination
                      }
                    },
...

The keys in the above query should be made dynamic, according to what is selected in the client-side Kibana Schema configuration.