Describe the requested update
We converted the format of the CXML Error Codes to support multiple causes in #586. We would like to go ahead and do the same stylistic update to the SignalWire REST API error codes.

Reason for the request
We would like to perform an audit of the SignalWire REST API endpoints and their errors soon, and we will likely need the same changes. We could get ahead of it by making the change now, even if only for the sake of consistency.

Sections to be updated
https://developer.signalwire.com/rest/signalwire-rest/overview/error-codes

Additional context
Add any other context or screenshots that might help understand the request.

Related Issues or PRs
https://github.com/signalwire/cloud-product/issues/16449
#586