Use Object.assign() instead of _.defaults()

lib/cartodb/cache/named_map_provider_cache.js

@@ -1,6 +1,5 @@
 'use strict';
 
-var _ = require('underscore');
 var NamedMapMapConfigProvider = require('../models/mapconfig/provider/named-map-provider');
 var templateName = require('../backends/template_maps').templateName;
 
@@ -70,12 +69,14 @@ function createNamedMapKey(user, templateId) {
 var providerKeyTpl = ctx => `${ctx.authToken}:${ctx.configHash}:${ctx.format}:${ctx.layer}:${ctx.scale_factor}`;
 
 function createProviderKey(config, authToken, params) {
-    var tplValues = _.defaults({}, params, {
+    const defaults = {
         authToken: authToken || '',
         configHash: NamedMapMapConfigProvider.configHash(config),
         layer: '',
         format: '',
         scale_factor: 1
-    });
-    return providerKeyTpl(tplValues);
+    };
+    const ctx = Object.assign({}, defaults, params);
+
+    return providerKeyTpl(ctx);
 }