/**
     * 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,

 *   <li>region - The AWS region (default: us-east-1)</li>
 *   <li>connectTimeout - Connection timeout in milliseconds (default: 10000)</li>
 *   <li>readTimeout - Read timeout in milliseconds (default: 10000)</li>
 * </ul>
 *
 * <p>The client supports URLs in the format: {@code s3://bucket-name/object-path}
 *
 * <p>Features:
 * <ul>
 *   <li>Automatic initialization of AWS S3 client</li>

                      properties:
                        label:
                          type: string
                          example: AWS
                        value:
                          type: string
                          example: aws
        '400':
          $ref: '#/components/responses/BadRequest'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '404':

     * 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. */