public void RemoveTransactionFromCategory(Guid transactionId, Guid categoryId)
        {
            var relationship = new CategoryToTransaction { TransactionId = transactionId, CategoryId = categoryId };

            db.Delete(relationship);
        }
        public void AddTransactionToCategory(Guid transactionId, Guid categoryId)
        {
            var relationship = new CategoryToTransaction { TransactionId = transactionId, CategoryId = categoryId };

            db.Insert(relationship);
        }