title: Laravel Request validation rename field
body: <p>I use pickadate.js and have a problem with the laravel validation. If I send the form with the datepicker to my application, then there are two fields. <code>birthday</code> and <code>birthday_submit</code>. The last is created by pickadate.js and contains the date in the following format: <code>yyyy/mm/dd</code>. </p>
  
  <p>My model has the column <code>birthday</code>. And my validation looks the following:</p>
  
  <pre class="lang-php prettyprint-override"><code>$request-&gt;validate([
              "first_name"=&gt;"required_without:last_name",
              "email"=&gt;"nullable|email",
              "birthday_submit"=&gt;"nullable|date"
          ]);
  </code></pre>
  
  <p>If I pass it to the <code>create()</code> function (Eloquent) then I get the error, that <code>birthday_submit</code> doesn't exist.</p>
  
  <p>Is there a way to rename <code>birthday_submit</code> to <code>birthday</code> so I can mass assign it? Also the error messages would be better because the user shouldn't get the error message that <code>birthday_submit</code> is invalid.</p>