public static BootstrapMetadata fromVersion(MetadataVersion metadataVersion, String source) {
        List<ApiMessageAndVersion> records = Collections.singletonList(
            new ApiMessageAndVersion(new FeatureLevelRecord().
                setName(MetadataVersion.FEATURE_NAME).
                setFeatureLevel(metadataVersion.featureLevel()), (short) 0));
        return new BootstrapMetadata(records, metadataVersion, source);
    }
The bootstrap metadata. On startup, if the metadata log is empty, we will populate the log with
these records. Alternately, if log is not empty, but the metadata version is not set, we will
use the version specified here.
metadata/src/main/java/org/apache/kafka/metadata/bootstrap/BootstrapMetadata.java