void dump() {
        StringBuilder sb = new StringBuilder().append("defaultSignerConfig: ").append(defaultSignerConfig).append("\n")
                .append("serviceRegionSigners: ").append(serviceRegionSigners).append("\n").append("regionSigners: ")
                .append(regionSigners).append("\n").append("serviceSigners: ").append(serviceSigners).append("\n")
                .append("userAgentTemplate: ").append(userAgentTemplate);
        log.debug(sb.toString());
    }
Remove duplicates from the provided list, while preserving the order of the elements in this list. We do this
manually instead of using a LinkedHashSet for the override URLs, because the set would invoke the URL's equals method.
URL's equals method requires a DNS query, which is not desired.
aws-java-sdk-core/src/main/java/com/amazonaws/internal/config/InternalConfig.java