graph/db: provide SQLStore with chainhash

In this commit, we introduce a SQLStoreConfig struct which for the time
being only has the ChainHash of the genesis block of the chain this node
is running on. This is used to reconstruct lnwire messages from what we
have persisted in the DB. This means we dont need need to persist the
chain-hash of gossip messages since we know it will always be the same
for a given node. If a node were to be started with a different network,
the lnwire messages it reconstructs for gossip will be invalid.

graph/db/test_postgres.go

@@ -6,6 +6,7 @@ import (
 	"database/sql"
 	"testing"
 
+	"github.com/btcsuite/btcd/chaincfg"
 	"github.com/lightningnetwork/lnd/kvdb"
 	"github.com/lightningnetwork/lnd/sqldb"
 	"github.com/stretchr/testify/require"
@@ -38,7 +39,11 @@ func NewTestDB(t testing.TB) V1Store {
 		},
 	)
 
-	store, err := NewSQLStore(executor, graphStore)
+	store, err := NewSQLStore(
+		&SQLStoreConfig{
+			ChainHash: *chaincfg.MainNetParams.GenesisHash,
+		}, executor, graphStore,
+	)
 	require.NoError(t, err)
 
 	return store