Enable Twilio request validation for Twilio Proxy

Twilio supports HTTP Basic and Digest Authentication but not Bearer [1], as required for Cloud Run.

This means users have to allow unauthenticated requests to use the Twilio Proxy.

Can we enable request validation [2] to reduce the security impact of this?

[1] https://www.twilio.com/docs/usage/security#http-authentication
[2] https://www.twilio.com/docs/usage/security#validating-requests