title: Convert to E164 only if possible?
body: <p>Can I determine if the user entered a phone number that can be safely formatted into E164?</p>
  
  <p>For Germany, this requires that the user started his entry with a local area code. For example, <code>123456</code> may be a subscriber number in his city, but it cannot be formatted into E164, because we don't know his local area code. Then I would like to keep the entry as it is. In contrast, the input <code>089123456</code> is independent of the area code and could be formatted into E164, because we know he's from Germany and we could convert this into <code>+4989123456</code>.</p>