* The identifier is composed of groupId, artifactId, extension, classifier, and version.
     *
     * @return the unique identifier
     */
    @Nonnull
    default String key() {
        return getGroupId()
                + ':'
                + getArtifactId()
                + ':'
                + getExtension()
                + (getClassifier().isEmpty() ? "" : ":" + getClassifier())