Function config_from_file 

pub fn config_from_file(
    path: impl AsRef<Path>,
) -> KafkaConfigResult<HashMap<String, String>>

Load librdkafka configuration from a file in the config git directory.

Detects format from file extension:

Extension	Format	Requires
.properties	Java-style key=value	nothing (always available)
.yaml, .yml	YAML flat mapping	directory-config feature
.json	JSON object	config feature

The returned map passes directly to merge_with_overrides or as librdkafka_overrides in KafkaConfig.

Errors

Returns KafkaConfigError if the file is missing, the format is unsupported, or parsing fails.