[Exchanges] handle MAX_FETCHED_OHLCV_COUNT

Trading/Exchange/okx/okx_exchange.py

@@ -112,6 +112,10 @@ class Okx(exchanges.RestExchange):
     DEFAULT_CONNECTOR_CLASS = OkxConnector
     MAX_PAGINATION_LIMIT: int = 100  # value from https://www.okex.com/docs/en/#spot-orders_pending
 
+    # set when the exchange returns nothing when fetching historical candles with a too early start time
+    # (will iterate historical OHLCV requests over this window)
+    MAX_FETCHED_OHLCV_COUNT = 100
+
     # Okx default take profits are market orders
     # note: use BUY_MARKET and SELL_MARKET since in reality those are conditional market orders, which behave the same
     # way as limit order but with higher fees