api - provide assset_currency via API

freqtrade/optimize/backtesting.py

@@ -726,6 +726,7 @@ class Backtesting:
 
         if stake_amount and (not min_stake_amount or stake_amount > min_stake_amount):
             self.order_id_counter += 1
+            base_currency = self.exchange.get_pair_base_currency(pair)
             amount = round((stake_amount / propose_rate) * leverage, 8)
             is_short = (direction == 'short')
             # Necessary for Margin trading. Disabled until support is enabled.
@@ -738,6 +739,8 @@ class Backtesting:
                     id=self.trade_id_counter,
                     open_order_id=self.order_id_counter,
                     pair=pair,
+                    base_currency=base_currency,
+                    stake_currency=self.config['stake_currency'],
                     open_rate=propose_rate,
                     open_rate_requested=propose_rate,
                     open_date=current_time,