BUGFIX Fix: Fix Phone Number Parsing for EU Numbers

Summary

If someone tries to add a phone number to a channel with a european number such as +49 9898989 (so without all the "-" and a different prefix than us, It retuns an error code like "must include prefix "+" etc.

Steps to reproduce

Using command "INVITE +49 98989898" With a valid phone number

What is the current behavior?

Returns error code

What is the expected correct behavior?

Adding to a channel

Or at least a part in the Documentation/Guide on how to format phone numbers