Support dial-out emergency numbers with SIP Bridge

[!TIP]

How to use GitHub

• Please use the 👍 reaction to show that you are affected by the same issue.
• Please don't comment if you have no relevant information to add. It's just extra noise for everyone subscribed to this issue.
• Subscribe to receive notifications on status change and new comments.

Feature request

Verify and implement support of calling local emergency / short numbers (911, 112, 116117, 103, e.t.c.)

Additional context
General:

• default_phone_region should be supplied in any case
• Emergency centers can ping caller location from the mobile device, how is could done via SIP?
  • E.g. if address of company might be registered, what if user is calling remotely?

Frontend:

• Requires a validation on client:
  • we can migrate from libphonenumber-js to google-libphonenumber to support validating short codes (larger library, but it's already async)

API:

• Check if number is modified in the process

SIP:

• Check if number is modified in the process
  • Quote: "The SIP bridge will call the number as received from Talk - but will evaluate any configured number-prefix or replace-prefixes from its server.conf."

Start by tracing client validation with libphonenumber-js, then follow how the API and SIP Bridge process numbers, including default_phone_region and the server.conf number-prefix or replace-prefixes settings. Compare short-code validation with google-libphonenumber and define done as emergency numbers being accepted and passed unchanged through the API and SIP flow, with location handling clarified.