title: How to auto populate email field on mfa page when display control is used in custom policies
body: <p>I have to use custom email template so I added a display control in my custom policy, now I have following issues because of this.</p>
  <ol>
  <li><p>When user logs in, mfa page with empty text box appears. I would like it to be auto populated.
  I followed the steps provided in <a href="https://stackoverflow.com/questions/54118940/populate-the-email-address-text-box-in-azure-ad-b2c-orchestration">Populate the email address text box in Azure AD B2C Orchestration</a>
  but seems like it doesn't work with dispaly control.</p>
  </li>
  <li><p>How to access/update &quot;extension_mfaByPhoneOrEmail&quot; field using ms graph api. I found one sample for this but it uses some id for &quot;extension_mfaByPhoneOrEmail&quot; which I could not find on azure portal. where I can get this id?
  &quot;https://graph.microsoft.com/v1.0/me/extensions/{{ExtensionId}}&quot;</p>
  </li>
  </ol>