getLicenseChallenge
abstract suspend fun getLicenseChallenge(sessionId: ByteString, pssh: PSSH, licenseType: LicenseType = LicenseType.STREAMING, privacyMode: Boolean = true, requestType: LicenseRequest.RequestType = LicenseRequest.RequestType.NEW): ByteArray
Build a signed license request for pssh.
Return
the serialized SignedMessage(LICENSE_REQUEST) to POST to a license server