Format all phone numbers according to E164

[jadudm]

From Twilio: https://www.twilio.com/docs/glossary/what-e164

From the wiki:

E.164 is an international standard (ITU-T Recommendation), titled The international public telecommunication numbering plan, that defines a numbering plan for the worldwide public switched telephone network (PSTN) and some other data networks.

We should store all phone numbers in this format, in the event that we ever need to handle numbers that are international. (We might have to already?)

https://ihateregex.io/expr/e164-phone/

https://support.secureauth.com/hc/en-us/articles/360036402211-Regular-Expressions-for-ITU-E-123-and-E-164-phone-number-formats

https://stackoverflow.com/questions/6478875/regular-expression-matching-e-164-formatted-phone-numbers

are starting points for patterns.

[jadudm]

Picked up in #1180. Referencing this for backwards tracking, but #1180 is a better place for the work.