Add functionality to create transactions

- Transactions work against the account balance
- Needs helper functions for users
- Needs more testing

controllers/accountController.js

@@ -36,6 +36,16 @@ exports.createAccount = (_discordAccountId, callback) => {
     })
 }
 
+exports.withdrawBalance = async (_withdrawAmount, _accountId, callback) => {
+    userStorage.updateBalance('withdraw', _withdrawAmount, _accountId, async (err, result) => {
+        if (err) return callback(err, undefined);
+
+        if(result) return callback(undefined, result);
+
+        return callback(undefined, undefined);
+    })
+}
+
 exports.verifyBalance = (_tokensToBeUsed, _accountId, callback) => {
     userStorage.checkBalance(_tokensToBeUsed, _accountId, (err, results) => {
         if (err) return callback(err, undefined);