Data layer restructuring (#997)

* Move query builders to sqlite package
* Add transaction system
* Wrap model resolvers in transaction
* Add error return value for StringSliceToIntSlice
* Update/refactor mutation resolvers
* Convert query builders
* Remove unused join types
* Add stash id unit tests
* Use WAL journal mode

pkg/models/model_scene_marker.go

@@ -13,3 +13,13 @@ type SceneMarker struct {
 	CreatedAt    SQLiteTimestamp `db:"created_at" json:"created_at"`
 	UpdatedAt    SQLiteTimestamp `db:"updated_at" json:"updated_at"`
 }
+
+type SceneMarkers []*SceneMarker
+
+func (m *SceneMarkers) Append(o interface{}) {
+	*m = append(*m, o.(*SceneMarker))
+}
+
+func (m *SceneMarkers) New() interface{} {
+	return &SceneMarker{}
+}