@Override
    protected void addSessionCredentials(SignableRequest<?> request,
            AWSSessionCredentials credentials) {
        request.addHeader("x-amz-security-token", credentials.getSessionToken());
    }
Constructs a new S3Signer to sign requests based on the Amazon Web Services credentials,
HTTP method and canonical S3 resource path.

@param httpVerb
           The HTTP verb (GET, PUT, POST, HEAD, DELETE) the request is
           using.
@param resourcePath
           The canonical S3 resource path (ex: "/", "/<bucket name>/", or
           "/<bucket name>/<key>".
@param additionalQueryParamsToSign
           A collection of user-specified query parameters that should be
           included in the canonical request, in addition to those
           default parameters that are always signed.

@see RestUtils#makeS3CanonicalString(String, String, Request, String)
aws-java-sdk-s3/src/main/java/com/amazonaws/services/s3/internal/S3Signer.java