Market data API: Add trade direction (buy/sell) to the "/api/trades" responses

[unbeaten69]

The responses provided by the https://markets.bisq.services/api/trades endpoint do not contain trade direction information (sell/buy) of individual trades at the moment.

The "industry standard" almost all exchanges seem to adhere to these days is to show the side from the taker point of view, in relation to the base token. It means that:

• for the BTC_USD market, maker sells BTC, taker buys BTC -> it's a BUY
• for the BTC_USD market, maker buys BTC, taker sells BTC -> it's a SELL
• for the XMR_BTC market, maker sells BTC, taker buys BTC -> it's a SELL
• for the XMR_BTC market, maker buys BTC, taker sells BTC -> it's a BUY

This piece of information can be useful for individuals who want to automate Bisq trading, for example it lets you see more easily whether the Bisq price diverges from the market price. Lets you see trends as well etc.