* Remove arbitrary SMS code
This code has run its course and is no longer needed for now.
* Add elements to sample config that were left out
* Add a messaging service for NANPA
* Fixup sample config capitalization
In preparation for resumable uploads, this creates a separate
attachment authorization endpoint that creates a signed URL for
accessing GCP Storage through Signal's CDN2. This should allow Signal
clients to do byte-level resume of media uploads.