public Builder customQueryParam(String name, String value) {
            customQueryParams.computeIfAbsent(name, key -> new ArrayList<>());
            customQueryParams.get(name).add(value);
            return this;
        }
Add a custom query parameter for the request. Since multiple values are allowed for the
same query parameter, this method does NOT overwrite any existing parameter values in the
request.

@param name  The name of the query parameter
@param value The value of the query parameter. Only the parameter name will be added in
             the URI if the value is set to null. For example, customQueryParameter("param",
             null) will be serialized to "?param", while customQueryParameter("param",
             "") will be serialized to "?param=".
@return This object for method chaining.
aws-java-sdk-opensdk/src/main/java/com/amazonaws/opensdk/SdkRequestConfig.java