Alignment of errors with Commonalities

Description of phone number identification based on   https://github.com/camaraproject/CallForwardingSignal/blob/main/code/API_definitions/Call_Forwarding_Signal.yaml

422_NOT_SUPPORTED -> when the service is not supported for the provided phone number (e.g. a B2B phone number)
UNIDENTIFIABLE_PHONE_NUMBER -> when the phone number is not provided in the request body a cannot be deducted from the access token. The UNIDENTIFIABLE_DEVICE should be used only when the API uses the object device

Co-authored-by: Fernando Prado Cabrillo <[email protected]>