add channel <type>:<id> appends an existing artifact to channels, by type and id, and never touches a number. At deploy, wireChannels in channels/wire.ts points the artifact’s webhook at the function and remembers the previous value, and one route for it goes into the list passed to channelRoutes in .telnyx/index.ts.
channels/index.ts serves every route at /webhooks/<type>/<id> and verifies each webhook against the account’s public key before reading it. A messaging_profile route runs messagingWebhook, a call_control_application route runs the call handler, and an email_domain route runs emailWebhook.