Replace `deepAssign` implementation with some lodash calls.

js/utils.js

@@ -365,25 +365,7 @@ function sortArrayByArray(sorted, unsorted, key) {
  * @param {object} source
  */
 function deepAssign(target, source) {
-	function isObject(o) {
-		return (o !== undefined && o !== null && typeof o === 'object' && !Array.isArray(o));
-	}
-
-	if (isObject(target) && isObject(source)) {
-		for (const key in source) {
-			if (!source.hasOwnProperty(key)) { continue; }
-			if (isObject(source[key])) {
-				if (!target.hasOwnProperty(key) || !isObject(target[key])) {
-					target[key] = {};
-				}
-				deepAssign(target[key], source[key]);
-			} else {
-				Object.assign(target, {
-					[key]: source[key]
-				});
-			}
-		}
-	}
+	_.assign(target, _.cloneDeep(source));
 }
 
 /**