Support for international phone numbers

Given an in-progress Platform application,
When I enter an international prefix (e.g. +44 for England)
and start typing in the phone number (e.g. XXXX-XXX-XXX for England),
Then the system prevents invalid inputs based on my prefix (see https://en.wikipedia.org/wiki/List_of_country_calling_codes).

Notes:
Perhaps there is an existing library/plug-in that we can leverage instead of building our own?

Start by locating the phone-number input and validation used by the Platform application, then check whether an existing international phone-number library is already available. Done means entering a country prefix constrains subsequent input to valid formats, including the England example, with appropriate validation coverage.

Written by the indexing model from the issue text.