TUN-8638: Add datagram v3 serializers and deserializers

Closes TUN-8638

quic/v3/request_test.go

@@ -0,0 +1,50 @@
+package v3_test
+
+import (
+	"crypto/rand"
+	"slices"
+	"testing"
+
+	v3 "github.com/cloudflare/cloudflared/quic/v3"
+)
+
+var (
+	testRequestIDBytes = [16]byte{
+		0x00, 0x11, 0x22, 0x33,
+		0x44, 0x55, 0x66, 0x77,
+		0x88, 0x99, 0xaa, 0xbb,
+		0xcc, 0xdd, 0xee, 0xff,
+	}
+	testRequestID = mustRequestID(testRequestIDBytes)
+)
+
+func mustRequestID(data [16]byte) v3.RequestID {
+	id, err := v3.RequestIDFromSlice(data[:])
+	if err != nil {
+		panic(err)
+	}
+	return id
+}
+
+func TestRequestIDParsing(t *testing.T) {
+	buf1 := make([]byte, 16)
+	n, err := rand.Read(buf1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if n != 16 {
+		t.Fatalf("did not read 16 bytes: %d", n)
+	}
+	id, err := v3.RequestIDFromSlice(buf1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	buf2 := make([]byte, 16)
+	err = id.MarshalBinaryTo(buf2)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !slices.Equal(buf1, buf2) {
+		t.Fatalf("buf1 != buf2: %+v %+v", buf1, buf2)
+	}
+}