change defaults

Author: aloiva

azure/functions/decorators/function_app.py

@@ -1246,7 +1246,7 @@ def kafka_trigger(self,
                       consumer_group: Optional[str] = None,
                       avro_schema: Optional[str] = None,
                       key_avro_schema: Optional[str] = None,
-                      key_data_type: Optional[Union[KafkaMessageKeyType, str]] = None,
+                      key_data_type: Optional[Union[KafkaMessageKeyType, str]] = KafkaMessageKeyType.STRING,
                       username: Optional[str] = None,
                       password: Optional[str] = None,
                       ssl_key_location: Optional[str] = None,
@@ -2607,7 +2607,7 @@ def kafka_output(self,
                      broker_list: str,
                      avro_schema: Optional[str] = None,
                      key_avro_schema: Optional[str] = None,
-                     key_data_type: Optional[Union[KafkaMessageKeyType, str]] = None,
+                     key_data_type: Optional[Union[KafkaMessageKeyType, str]] = KafkaMessageKeyType.STRING,
                      username: Optional[str] = None,
                      password: Optional[str] = None,
                      ssl_key_location: Optional[str] = None,