These must provide `msgp` serialization and deserialization.

In the examples we use a `MSS` type, which is a `map[string]string` that is `msgp` serializable.

```go
    handler := func(request *grid.MSS) (*grid.MSS, *grid.RemoteErr) {
        fmt.Println("Got request with field", request["myfield"])
        // Do something with payload

		v[i] = zero
	}
	if v != nil {
		v = v[:0]
		p.aPool.Put(&v)
	}
}

func (p *ArrayOf[T]) newE() T {
	return p.ePool.Get().(T)
}

// Array provides a wrapper for an underlying array of serializable objects.
type Array[T RoundTripper] struct {
	p   *ArrayOf[T]
	val []T
}

// Msgsize returns the size of the array in bytes.
func (j *Array[T]) Msgsize() int {
	if j.val == nil {