Constrain log length for CBC proxy payload

This avoids any issues due to large payloads (e.g. with a lot of
polygons in the 'areas' field). While we may miss part of the log
in such cases, this is more than we get already anyway.

app/clients/cbc_proxy.py

@@ -123,7 +123,7 @@ class CBCProxyClientBase(ABC):
         payload_bytes = bytes(json.dumps(payload), encoding='utf8')
         try:
             current_app.logger.info(
-                f"Calling lambda {lambda_name} with payload {payload}"
+                f"Calling lambda {lambda_name} with payload {str(payload)[:1000]}"
             )
 
             result = self._lambda_client.invoke(