in callouts/java/service-callout/src/main/java/example/BasicCalloutServer.java [71:82]
public void onRequestHeaders(ProcessingResponse.Builder processingResponseBuilder,
HttpHeaders headers) {
// Modify headers for the request
addHeaderMutations(
processingResponseBuilder.getRequestHeadersBuilder(),
ImmutableMap.of("request-header", "added-request", "c", "d").entrySet(), // Headers to add
null, // No headers to remove
true, // Clear route cache
null // No append action
);
}