title: Ra-data-simple-rest is not working | ERROR: total is not a number and newRecords.forEach is not a function
body: <p>I am trying to follow the tutorial and I am now at the part where I have to implement
  my own REST-API. My format is identical to the needed format described in the tutorial.
  Here my response: <a href="https://i.stack.imgur.com/jjqbd.png" rel="nofollow noreferrer">The response from my API</a></p>
  
  <p>The needed format looks like this: </p>
  
  <pre><code>// {
  //     data: [
  //         { id: 126, title: "allo?", author_id: 12 },
  //         { id: 127, title: "bien le bonjour", author_id: 12 },
  //         { id: 124, title: "good day sunshine", author_id: 12 },
  //         { id: 123, title: "hello, world", author_id: 12 },
  //         { id: 125, title: "howdy partner", author_id: 12 },
  //     ],
  //     total: 27
  // }
  </code></pre>
  
  <p>But for some reason I always get the error that (1) total is not a number, but postman says it is. And (2) that newRecords.forEach is not a function.</p>
  
  <p>´´´</p>
  
  <pre><code>//App.js
  import logo from './logo.svg';
  import React from 'react';
  import { Admin, Resource, ListGuesser } from 'react-admin';
  import simpleRestProvider from 'ra-data-simple-rest';
  import styles from './App.css';
  import SimpleFlow from './diagramm';
  import { RuleList, PostList} from './rules';
  
  //http://jsonplaceholder.typicode.com'
  const dataProvider = simpleRestProvider('http://localhost:3000/api');
  const App = () =&gt;
      &lt;Admin dataProvider={dataProvider} dashboard={SimpleFlow}&gt;
          &lt;Resource name="rules" list={RuleList} /&gt;
      &lt;/Admin&gt;;
  
  export default App;
  </code></pre>
  
  <p>´´´</p>
  
  <p>´´´</p>
  
  <pre><code>//rules.js
  import React from 'react';
  import { List, Datagrid, TextField, EmailField, DateField, Pagination } from 'react-admin'; 
  
  export const RuleList = (props) =&gt; (
      &lt;List {...props} perPage={25}&gt;
          &lt;Datagrid rowClick="edit"&gt;
              &lt;TextField source="id" /&gt;
              &lt;TextField source="Bezeichnung" /&gt;
          &lt;/Datagrid&gt;
      &lt;/List&gt;
  
  );
  </code></pre>
  
  <p>´´´</p>