public ChangeMessageBuilder addChange(String component, String from, String to) {
        changes.add(component + ": '" + from + "' -> '" + to + "'");
        return this;
    }
Builder of a message describing the changes in a given field.

@author geirst
config-model/src/main/java/com/yahoo/vespa/model/application/validation/change/search/ChangeMessageBuilder.java