Function render_metadata_fetcher 

fn render_metadata_fetcher<'scope>(
    scope: Scope<'scope, KafkaTimestamp>,
    connection: KafkaSourceConnection,
    config: RawSourceCreationConfig,
) -> (StreamVec<'scope, KafkaTimestamp, (Timestamp, MetadataUpdate)>, StreamVec<'scope, KafkaTimestamp, Probe<KafkaTimestamp>>, PressOnDropButton)

Render the metadata fetcher of a Kafka source.

The metadata fetcher is a single-worker operator that is responsible for periodically fetching the Kafka topic metadata (partition IDs and high watermarks) and making it available as a Timely stream.