code: @Nullable
    public IUser getUserOfEmailAddressIgnoreCase (@Nullable final String sEmailAddress)
    {
      if (StringHelper.hasNoText (sEmailAddress))
        return null;
  
      return findFirst (x -> sEmailAddress.equalsIgnoreCase (x.getEmailAddress ()));
    }
docs: Get the user with the specified email address
  
  @param sEmailAddress
  The email address to be checked. May be <code>null</code>.
  @return <code>null</code> if no such user exists
  @see #getUserOfEmailAddress(String)
  @since 8.1.3