Update backend and data model to interact with smart contract for P2P auctions

Proposed model, based on @davidjmurphyjr's comment in #212:

CollectibleAuction

id guid - primary key
collectibleId guid - foreign key to a collectible
userAccountId guid - foreign key to a user account (represents the seller)
reservePrice int - minimum bid amount in microAlgos
startAt datetime with tz - start date + time bids are allowed to be made
endAt datetime with tz - end date + time bids are no longer allowed and auction is closed
createdAt datetime with tz - date listing was created
status active | closing | closed | canceled - some statuses to help with background tasks
appId int - the blockchain app (smart contract) ID
activeBidId guid - optional field for the current top bid
transactionId guid - foreign key to an algorand transaction for the app creation transaction

id guid - primary key
collectibleAuctionId guid - foreign key to a listing
amount int - bid in microAlgos
userAccountId guid - foreign key to a user account (represents the bidder)
createdAt datetime with tz - date bid was made
transactionId guid - optional foreign key to an algorand transaction for the payment or app call transaction