Export Client constants for external use (#83)

The API Client currently enforces constraints on price and quantity,
such as bounds on their values and the number of allowed decimal places.
This PR introduces the ability to export the constants defining these
constraints, enabling applications using the API to reference them
directly.

Author: camille-bouvy-frequenz

RELEASE_NOTES.md

@@ -15,6 +15,7 @@
 * Add more edge cases to the integration tests.
 * Add idiomatic string representations for `Power` and `Price` classes.
 * Add support for timeouts in the gRPC function calls
+* Export Client constants for external use
 
 ## Bug Fixes
 

src/frequenz/client/electricity_trading/__init__.py

@@ -179,7 +179,14 @@ async def stream_trades():
 
 """
 
-from ._client import Client
+from ._client import (
+    MAX_PRICE,
+    MIN_PRICE,
+    MIN_QUANTITY_MW,
+    PRECISION_DECIMAL_PRICE,
+    PRECISION_DECIMAL_QUANTITY,
+    Client,
+)
 from ._types import (
     Currency,
     DeliveryArea,
@@ -231,4 +238,9 @@ async def stream_trades():
     "StateReason",
     "Trade",
     "TradeState",
+    "MAX_PRICE",
+    "MIN_PRICE",
+    "MIN_QUANTITY_MW",
+    "PRECISION_DECIMAL_QUANTITY",
+    "PRECISION_DECIMAL_PRICE",
 ]