[SalesForce] Get username using Lightning Data Service

I wish there was concept like merge field in Lightning components where some functions were global and directly accessible but looks like only way to do this will be code with server side call.

Below is sample code

public with sharing class SimpleServerSideController {

//Use @AuraEnabled to enable client- and server-side access to the method
  @AuraEnabled
  public static String getUserName() {
    return userinfo.getName();
  }
 }

<aura:component controller="SimpleServerSideController">
   <aura:attribute name="Name" type="String"/>
   <aura:handler name="init" value="{!this}" action="{!c.doInit}"/>
</aura:component>

({
doInit: function(cmp){
    var action = cmp.get("c.getUserName");
    action.setCallback(this, function(response){
        var state = response.getState();
        if (state === "SUCCESS") {
            cmp.set("v.Name", response.getReturnValue());
         }
      });
       $A.enqueueAction(action);
     }
 })

Using the Lightning Data Service - Considerations page as reference, it appears that currently you are able to work with data across spanning relationships (lookup, master-detail) but not collections of records (subquery).

Lightning Data Service supports primitive DML operations—create, read, update, and delete. It operates on one record at a time, which you retrieve or modify using the record ID. Lightning Data Service supports spanned fields with a maximum depth of five levels. Support for working with collections of records or for querying for a record by anything other than the record ID isn’t available. If you must support higher-level operations or multiple operations in one transaction, use standard @AuraEnabled Apex methods.