title: Django Emailfield fixed suffix
body: <p>In my Contact model I use an EmailField to assure I'm saving a valid email address.</p>
  
  <p>In my form however, I only want the user to be able to change the part before the <code>@</code>, the domain part is not user defined. (e.g. every email needs to end with <code>@gmail.com</code>)</p>
  
  <p>I have looked at a lot of questions about modifying Django form field values before and after validation and display phase, but a lot of the answers are kind of 'hacky' or seem to much of a workaround for my case.</p>
  
  <p>Is there some support of kind of a display filter, which manages a fixed prefix/suffix of a Django form field, without having to edit POST values or needing to suppress certain validations?</p>