String task4(AwsSigner4Request sr, AuthConfig credentials) {
        StringBuilder sb = new StringBuilder("AWS4-HMAC-SHA256 Credential=")
                .append(credentials.getUsername() ).append( '/' ).append( sr.getScope() )
                .append(", SignedHeaders=").append(sr.getSignedHeaders())
                .append(", Signature=" );
        hexEncode(sb, task3(sr, credentials));
        return sb.toString();
    }
Task 4.
<a href="https://docs.aws.amazon.com/general/latest/gr/sigv4-add-signature-to-request.html">Add the Signing Information to the Request</a>
src/main/java/io/fabric8/maven/docker/access/ecr/AwsSigner4.java