contractcourt: add HtlcBlobs to taprootBriefcase

In this commit, we add the set of HtlcBlobs to the taprootBriefcase
struct. This new field will store all the resolution blobs for a given
HTLC. We also add some new property based tests along the way for
adequate test coverage.

contractcourt/taproot_briefcase_test.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/lightningnetwork/lnd/tlv"
 	"github.com/stretchr/testify/require"
+	"pgregory.net/rapid"
 )
 
 func randResolverCtrlBlocks(t *testing.T) resolverCtrlBlocks {
@@ -53,6 +54,25 @@ func randHtlcTweaks(t *testing.T) htlcTapTweaks {
 	return tweaks
 }
 
+func randHtlcAuxBlobs(t *testing.T) htlcAuxBlobs {
+	numBlobs := rand.Int() % 256
+	blobs := make(htlcAuxBlobs, numBlobs)
+
+	for i := 0; i < numBlobs; i++ {
+		var id resolverID
+		_, err := rand.Read(id[:])
+		require.NoError(t, err)
+
+		var blob [100]byte
+		_, err = rand.Read(blob[:])
+		require.NoError(t, err)
+
+		blobs[id] = blob[:]
+	}
+
+	return blobs
+}
+
 // TestTaprootBriefcase tests the encode/decode methods of the taproot
 // briefcase extension.
 func TestTaprootBriefcase(t *testing.T) {
@@ -93,6 +113,9 @@ func TestTaprootBriefcase(t *testing.T) {
 		BreachedCommitBlob: tlv.SomeRecordT(
 			tlv.NewPrimitiveRecord[tlv.TlvType3](commitBlob[:]),
 		),
+		HtlcBlobs: tlv.SomeRecordT(
+			tlv.NewRecordT[tlv.TlvType4](randHtlcAuxBlobs(t)),
+		),
 	}
 
 	var b bytes.Buffer
@@ -103,3 +126,21 @@ func TestTaprootBriefcase(t *testing.T) {
 
 	require.Equal(t, testCase, &decodedCase)
 }
+
+// TestHtlcAuxBlobEncodeDecode tests the encode/decode methods of the HTLC aux
+// blobs.
+func TestHtlcAuxBlobEncodeDecode(t *testing.T) {
+	t.Parallel()
+
+	rapid.Check(t, func(t *rapid.T) {
+		htlcBlobs := rapid.Make[htlcAuxBlobs]().Draw(t, "htlcAuxBlobs")
+
+		var b bytes.Buffer
+		require.NoError(t, htlcBlobs.Encode(&b))
+
+		decodedBlobs := newAuxHtlcBlobs()
+		require.NoError(t, decodedBlobs.Decode(&b))
+
+		require.Equal(t, htlcBlobs, decodedBlobs)
+	})
+}