watchtower/blob/justice_kit: add BlobType to JusticeKit struct

This is preparation for later commits where the values returned by
member methods will need to be conditioned on the blob type used during
decryption.

watchtower/blob/justice_kit_test.go

@@ -150,6 +150,7 @@ func TestBlobJusticeKitEncryptDecrypt(t *testing.T) {
 
 func testBlobJusticeKitEncryptDecrypt(t *testing.T, test descriptorTest) {
 	boj := &blob.JusticeKit{
+		BlobType:             test.encVersion,
 		SweepAddress:         test.sweepAddr,
 		RevocationPubKey:     test.revPubKey,
 		LocalDelayPubKey:     test.delayPubKey,
@@ -170,7 +171,7 @@ func testBlobJusticeKitEncryptDecrypt(t *testing.T, test descriptorTest) {
 
 	// Encrypt the blob plaintext using the generated key and
 	// target version for this test.
-	ctxt, err := boj.Encrypt(key, test.encVersion)
+	ctxt, err := boj.Encrypt(key)
 	if err != test.encErr {
 		t.Fatalf("unable to encrypt blob: %v", err)
 	} else if test.encErr != nil {