public ConfigurationImage apply() {
        Map<String, String> newData = new HashMap<>(image.data().size());
        for (Entry<String, String> entry : image.data().entrySet()) {
            Optional<String> change = changes.get(entry.getKey());
            if (change == null) {
                newData.put(entry.getKey(), entry.getValue());
            } else if (change.isPresent()) {
                newData.put(entry.getKey(), change.get());
            }
        }
        for (Entry<String, Optional<String>> entry : changes.entrySet()) {
            if (!newData.containsKey(entry.getKey())) {
                if (entry.getValue().isPresent()) {
                    newData.put(entry.getKey(), entry.getValue().get());
                }
            }
        }
        return new ConfigurationImage(image.resource(), newData);
    }
Represents changes to the configurations in the metadata image.
metadata/src/main/java/org/apache/kafka/image/ConfigurationDelta.java