DB models

[posgnu]

A back-end of the DEX should be able to relay orders and keep them until the taker who wants to fill or partially fill the order appears. We need a model for orders which will be referred to an order book.

Order
  makerAsset: String,
  takerAsset: String,
  amount: Bigint,
  rate: Double,
  makerAddress: String,
  assetList: JSON
  order: JSON
  marketId: number

Except for the transaction field, other fields are only for querying transaction. These are also in the transaction.
Also, a model for the history of completed transactions is needed for future reference.

Deal
  maker: String,
  taker: String,
  makerAsset: String,
  takerAsset: String,
  makerAmount: Integer,
  takerAmount: Integer,

DB have to be changed according to changed matching scheme