This function takes a phone number and formats it in accordance with world standard ITU-T E.123.
If the supplied phone number has a leading plus (+) character then the number will be formatted as an international number, otherwise as a national number.
If a default country code is supplied then all numbers will be formatted as international numbers regardless of original format.
Note: Only phone numbers deemed valid by the function SoftadminUtil.PhoneNumber_IsValid are guaranteed to be formatted correctly.
A formatted phone number.