graph/db: make all ExtraOpaqueData valid TLV streams

Later when we introduce our SQL version of the graph store, we will
normalise the persistence of the ExtraOpaqueData using the fact that it
is always made up of TLV entries. So we update our tests here to ensure
that they use valid TLV streams as examples.

graph/db/graph_test.go

@@ -110,7 +110,7 @@ func TestNodeInsertionAndDeletion(t *testing.T) {
 		Alias:                "kek",
 		Features:             testFeatures,
 		Addresses:            testAddrs,
-		ExtraOpaqueData:      []byte("extra new data"),
+		ExtraOpaqueData:      []byte{1, 1, 1, 2, 2, 2, 2},
 		PubKeyBytes:          testPub,
 	}
 
@@ -631,9 +631,13 @@ func createChannelEdge(node1, node2 *models.LightningNode) (
 			BitcoinSig1Bytes: testSig.Serialize(),
 			BitcoinSig2Bytes: testSig.Serialize(),
 		},
-		ChannelPoint:    outpoint,
-		Capacity:        1000,
-		ExtraOpaqueData: []byte("new unknown feature"),
+		ChannelPoint: outpoint,
+		Capacity:     1000,
+		ExtraOpaqueData: []byte{
+			1, 1, 1,
+			2, 2, 2, 2,
+			3, 3, 3, 3, 3,
+		},
 	}
 	copy(edgeInfo.NodeKey1Bytes[:], firstNode[:])
 	copy(edgeInfo.NodeKey2Bytes[:], secondNode[:])