@Override
    public String toString() {
        StringBuilder sb = new StringBuilder("url: ")
                .append(url)
                .append("\nproperties:\n")
                .append(StringUtils.indent(properties.toString(), 2));
        for (Map.Entry<String, List<String>> entry : headers.entrySet()) {
            sb.append(StringUtils.indent(String.format("%s:%s", entry.getKey(), entry.getValue()), 2));
        }
        return sb.toString();
    }
Gets the headers to set when sending HTTP requests to the URL.

@return a map of header names to a list of values to set on those headers.
smithy-rules-engine/src/main/java/software/amazon/smithy/rulesengine/language/evaluation/value/EndpointValue.java