BetaOptional BetacallCustom headers sent in the call setup as SVAML extra info. At most 16 headers; each key must be a valid
SIP header name (letters, digits and the characters -.!%*_+'~ plus backtick) of at most 255 characters,
and each value at most 255 characters.
Optional BetaserviceIdentifier of a Sinch Voice V2 Service whose configuration (webhooks, signing credentials, call behaviours) governs the dial. When omitted, the project's default Service is used.
Optional BetatransportSIP transport protocol.
Options for dialing a SIP destination through the Sinch Voice V2 platform.