sqldb: define schemas for all graph node tables

In this commit, the various SQL schemas required to store graph node
related data is defined. Specifically, the following tables are defined:

- nodes
- node_extra_types
- node_features
- node_addresses

sqldb/sqlc/models.go

@@ -102,3 +102,31 @@ type MigrationTracker struct {
 	Version       int32
 	MigrationTime time.Time
 }
+
+type Node struct {
+	ID         int64
+	Version    int16
+	PubKey     []byte
+	Alias      sql.NullString
+	LastUpdate sql.NullInt64
+	Color      sql.NullString
+	Signature  []byte
+}
+
+type NodeAddress struct {
+	NodeID   int64
+	Type     int16
+	Position int32
+	Address  string
+}
+
+type NodeExtraType struct {
+	NodeID int64
+	Type   int64
+	Value  []byte
+}
+
+type NodeFeature struct {
+	NodeID     int64
+	FeatureBit int32
+}