Core e-Commerce module implements two transaction types: 'ec_buynow' and 'ec_cart', each one is implemented in the modules with the same name.

The way I see that, example of transaction types are 'donation', 'refund', 'payout', 'purchase', etc. So e.g. 'ec_cart' doesn't 'fit' in this list.

I propose we change that so to provide a single transaction type: 'purchase' in ec_product or ec_store module, ec_product makes more sense to me since I see sense in moving ec_transaction_products table to there as well (I will file another issue for that).