Trade: Persist trades in the database

using atomic transactions.
If a card happens to not be owned by the trading user, the entire
trade is being rolled back.
Rollback behaviour is a bit weird though, since we have to rollback
manually even in a managed transaction.

util/general.js

@@ -1,4 +1,6 @@
 const { Bot } = require("../models");
+const crypto = require("crypto");
+const { ReactionUserManager } = require("discord.js");
 
 module.exports = {
     name: "GeneralUtils",
@@ -11,5 +13,9 @@ module.exports = {
         let bot = await Bot.findOne();
         bot[property] = value;
         await bot.save();
+    },
+
+    generateLogID: async function() {
+        return crypto.randomBytes(4).toString("hex");
     }
 }