Be able to aggregate by a field

lib/cartodb/api/map/clustered-features-layergroup-controller.js

@@ -43,7 +43,7 @@ module.exports = class AggregatedFeaturesLayergroupController {
             authorize(this.authBackend),
             dbConnSetup(this.pgConnection),
             rateLimit(this.userLimitsBackend, RATE_LIMIT_ENDPOINTS_GROUPS.ATTRIBUTES),
-            cleanUpQueryParams(),
+            cleanUpQueryParams([ 'aggregation' ]),
             createMapStoreMapConfigProvider(
                 this.mapStore,
                 this.userLimitsBackend,
@@ -67,11 +67,13 @@ function getClusteredFeatures (clusterBackend) {
         const { user, token } = res.locals;
         const { dbuser, dbname, dbpassword, dbhost, dbport } = res.locals;
         const { layer, z: zoom, clusterId } = req.params;
+        const { aggregation } = req.query;
 
         const params = {
             user, token,
             dbuser, dbname, dbpassword, dbhost, dbport,
-            layer, zoom, clusterId
+            layer, zoom, clusterId,
+            aggregation
         };
 
         clusterBackend.getClusterFeatures(mapConfigProvider, params, (err, features, stats = {}) => {