Use only safe phone numbers in demo content

Problem/Motivation

In the person recipe we're currently using the phone number +2 345 678 901 which is unlikely to be valid, but since Nigeria has the country code +234 it's not impossible.

Proposed resolution

Let's be on the safe side and only use globally allocated fictitious phone numbers, see https://en.wikipedia.org/wiki/Fictitious_telephone_number

As a policy for demo content and for documentation, this should be somehow governed in general, also for e.g. IP addresses or domain names, which is often an issue. This is nicely explained in an article at https://www.cloudfoundry.org/blog/domains-and-ip-addresses-reserved-for-...