HttpGatewayServlet causes ClassCastException because it can process only headers with List<String> value.
https://github.com/jboss-switchyard/components/blob/2.0.0.Alpha2/http/src/main/java/org/switchyard/component/http/HttpGatewayServlet.java#L166

Issue is connected with contextMapper. If we use regular expression in includes attribute with value ".*" it will add to HTTP response various types.

e.g. Following code appends header of type List<DefaultMessageHistory>
https://github.com/apache/camel/blob/camel-2.12.2/camel-core/src/main/java/org/apache/camel/processor/CamelInternalProcessor.java#L681
This will cause the following exception:
java.lang.ClassCastException: org.apache.camel.impl.DefaultMessageHistory cannot be cast to java.lang.String