Validate phone numbers

[patcon]

Could theoretically use the twilio api to screen out certain types of phone numbers:
https://www.twilio.com/lookup

Login.gov allows any number for initial account creation, but requires a "real" phone number (not sure their definition) during the verify step. Our custom proofer just accepts any number.

In theory, we could lock out voip type numbers, and perhaps only accept numbers that validate with a canadian MCC of 302. Or perhaps a known MNC, because while Google Voice lacks a MCC, voip.ms seems to have one, but does conspicuously lack a network code (MNC).