Add MessageBodyWriter for ParticipantStatus and application/octet-stream media type

application/octet-stream is the default media type in RESTEasy which is used when @Produces value is not specified. We are always expecting String values from LRA participant methods so instead of requiring @Produces(MediaType.TEXT_PLAIN) on each @Compensate, @Complete, @Status, etc. methods we can include MessageBodyWriter<ParticipantStatus> implementation in narayana-lra module which will just transform ParticipantStatus value to String.