payload

fun payload(el: String, clazz: Class<Req>): GrpcCallActionBuilder<Req, Res>
fun payload(body: Req): GrpcCallActionBuilder<Req, Res>
fun payload(f: Function<Session, Req>): GrpcCallActionBuilder<Req, Res>
inline fun payload(crossinline f: (Session) -> Req): GrpcCallActionBuilder<Req, Res>