Ensure timestamp conversion errors are surfaced (#133)

Added a try...except...raise block around the calls to
`dt_to_pb_timestamp_utc` for start_time and end_time.

Previously, an error during this conversion might not have been handled
explicitly at this point. This change guarantees that if the conversion
fails, the exception is propagated immediately, improving robustness and
aiding debugging by making the failure point clear.

Author: matthias-wende-frequenz

RELEASE_NOTES.md

@@ -6,19 +6,12 @@
 
 ## Upgrading
 
-* Unify Public Trades streaming and listing (to align with the proto changes in v0.5.0)
-    * Removed `list_public_trades`
-    * Replaced `public_trades_stream` with `receive_public_trades`
-    * `receive_public_trades` now supports an optional time range (`start_time`, `end_time`)
-* Update the `frequenz-api-electricity-trading` from >= 0.5.0, < 0.6.0 to >= 0.6.1, < 0.7.0
-* Update repo-config from v0.11.0 to v0.13.0
+<!-- Here goes notes on how to upgrade from previous versions, including deprecations and what they should be replaced with -->
 
 ## New Features
 
-* Add the Public Order Book extension to the client
-    * Add the `PublicOrder` and `PublicOrderFilter` types
-    * Add the `receive_public_order()` endpoint
+<!-- Here goes the main new features and examples or instructions on how to use them -->
 
 ## Bug Fixes
 
-<!-- Here goes notable bug fixes that are worth a special mention or explanation -->
+- Ensure timestamp conversion errors are surfaced

src/frequenz/client/electricity_trading/_client.py

@@ -1036,6 +1036,9 @@ def receive_public_order_book(
             side=side,
         )
 
+        start_time_utc = dt_to_pb_timestamp_utc(start_time) if start_time else None
+        end_time_utc = dt_to_pb_timestamp_utc(end_time) if end_time else None
+
         if (
             public_order_filter not in self._public_orders_streams
             or not self._public_orders_streams[public_order_filter].is_running
@@ -1047,16 +1050,8 @@ def receive_public_order_book(
                         lambda: self.stub.ReceivePublicOrderBookStream(
                             electricity_trading_pb2.ReceivePublicOrderBookStreamRequest(
                                 filter=public_order_filter.to_pb(),
-                                start_time=(
-                                    dt_to_pb_timestamp_utc(start_time)
-                                    if start_time
-                                    else None
-                                ),
-                                end_time=(
-                                    dt_to_pb_timestamp_utc(end_time)
-                                    if end_time
-                                    else None
-                                ),
+                                start_time=start_time_utc,
+                                end_time=end_time_utc,
                             ),
                             metadata=self._metadata,
                         ),