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_movie.go

@@ -50,3 +50,13 @@ func NewMovie(name string) *Movie {
 		UpdatedAt: SQLiteTimestamp{Timestamp: currentTime},
 	}
 }
+
+type Movies []*Movie
+
+func (m *Movies) Append(o interface{}) {
+	*m = append(*m, o.(*Movie))
+}
+
+func (m *Movies) New() interface{} {
+	return &Movie{}
+}