/**
     * Creates a new S3StorageClient instance.
     *
     * @param endpoint the S3 endpoint URL (null for AWS default)
     * @param accessKey the AWS access key
     * @param secretKey the AWS secret key
     * @param bucket the bucket name
     * @param region the AWS region
     */
    public S3StorageClient(final String endpoint, final String accessKey, final String secretKey, final String bucket,

     * @return detected storage type
     */
    public static StorageType detectStorageType(final String endpoint) {
        if (StringUtil.isBlank(endpoint)) {
            // Default to S3 if no endpoint (uses AWS default)
            return StorageType.S3;
        }

        final String lowerEndpoint = endpoint.toLowerCase(Locale.ROOT);

        // GCS patterns

     * Storage type for cloud storage (s3, gcs, auto).
     * Determines which storage client to use.
     */
    @Size(max = 20)
    public String storageType;

    /**
     * Storage region for S3.
     * AWS region where the S3 bucket is located.
     */
    @Size(max = 100)
    public String storageRegion;

    /**
     * GCS project ID.
     * Google Cloud project ID for GCS storage.
     */

    // ============================================================

    /** Cloud-based search engine type. */
    public static final String FESEN_TYPE_CLOUD = "cloud";

    /** AWS-based search engine type. */
    public static final String FESEN_TYPE_AWS = "aws";

    /** Search engine username configuration key. */
    public static final String FESEN_USERNAME = "fesen.username";

    /** Search engine password configuration key. */