title: Change of TextInput value on Admin-on-Rest before validation?
body: <p>On <code>admin-on-rest</code>, how can we use the onChange handler to change the value of a TextInput while typing (i.e. before validation)?</p>
  
  <p>See example:</p>
  
  <pre><code>const handleChange = (e, newValue) =&gt; {
      const value = newValue.toUpperCase();
      // ???? How do we inform the TextInput of the new value, since we do not have a state inside this component but only in REDUX? 
  };
  </code></pre>
  
  <p>...</p>
  
  <pre><code> &lt;Edit title={&lt;TitleEdit /&gt;} {...props}&gt;
      &lt;SimpleForm validate={validateCreateEdit}&gt;
          &lt;TextInput label="BRAND" source="brand" onChange={handleChange.bind(this)} /&gt;
      &lt;/SimpleForm&gt;
  &lt;/Edit&gt;
  </code></pre>
  
  <p>Thanks.</p>