@Override
    public String toString() {
        return checksums.values().stream()
                        .map(checksum -> checksum.type().name() + ":" + checksum.asString())
                        .collect(Collectors.joining(","));
    }
Checksums for config payload, typically 1 for each PayloadChecksum type (md5 and xxhash64).
Initialized with empty checksum for each existing type.

@author hmusum
config/src/main/java/com/yahoo/vespa/config/PayloadChecksums.java