Invalid bids and user cash withdrawal about cs50_commerce HOT 3 CLOSED

Intended behavior depends on other tickets

• New bids should be validated by the form
• New bids should only be accepted if they are greater than the value of previous bids (currently accepts equal to)
• New bids should not call validation before the required user and listing objects can be attached to the bound bid form/bid object

from cs50_commerce.

limiting the scope of this ticket to correcting the buggy behavior around new bids:

• refactored the Bid.highest_current_bid() function for clarity
• corrected buggy behavior by implementing a validator on the Bid.bid property
• Added control flow to BidForm submissions so that new bids must exceed the Bid.highest_current_bid() value

from cs50_commerce.

noting that Bid.bid validation (outside of modelforms) also broke as a result of this refactor. I've moved back to strictly validating against submitting negative bids within the Bid.save function.

Why? Some form of guardrails should be in place whenever money (or similar serious issues such as lives being at stake) is manipulated/transacted - even if it's fake money.

from cs50_commerce.