Added ECB converter 2

Author: jbaron

roboquant/brokers/simbroker.py

@@ -182,7 +182,7 @@ def _calculate_short_positions(self):
             reserved += short_value
         return reserved
 
-    def _calculate_buyingpower(self):
+    def _calculate_buyingpower(self) -> Amount:
         """Calculate buying power, based on:
 
         buying_power = cash - open_orders - short_positions

roboquant/monetary.py

@@ -23,6 +23,9 @@ def __rmatmul__(self, other: float | int):
         assert isinstance(other, (float, int))
         return Amount(self, other)
 
+    def __call__(self, other: float | int):
+        return Amount(self, other)
+
 
 # Commonly used currencies
 USD = Currency("USD")
@@ -48,6 +51,10 @@ def convert(self, amount: "Amount", to_currency: Currency, time: datetime) -> fl
         """Convert the monetary amount into another currency at the provided time."""
         ...
 
+    def register(self):
+        """Register this converter to be used for conversions between amounts"""
+        Amount.register_converter(self)
+
 
 class NoConversion(CurrencyConverter):
     """The default currency converter that doesn't convert between currencies"""