Add bulk allowance edit endpoint (#56)

Closes #15

Reviewed-on: #56

backend/db.go

@@ -251,6 +251,31 @@ func (db *Db) UpdateAllowance(userId int, allowanceId int, allowance *UpdateAllo
 	return tx.Commit()
 }
 
+func (db *Db) BulkUpdateAllowance(userId int, allowances []BulkUpdateAllowanceRequest) error {
+	tx, err := db.db.Begin()
+	if err != nil {
+		return err
+	}
+	defer tx.MustRollback()
+
+	for _, allowance := range allowances {
+		if allowance.ID == 0 {
+			err = tx.Query("update users set weight=? where id = ?").
+				Bind(allowance.Weight, userId).
+				Exec()
+		} else {
+			err = tx.Query("update allowances set weight=? where id = ? and user_id = ?").
+				Bind(allowance.Weight, allowance.ID, userId).
+				Exec()
+		}
+		if err != nil {
+			return err
+		}
+	}
+
+	return tx.Commit()
+}
+
 func (db *Db) CreateTask(task *CreateTaskRequest) (int, error) {
 	tx, err := db.db.Begin()
 	if err != nil {