in invoker/core/src/main/java/com/google/cloud/functions/invoker/CloudEvents.java [283:294]
Event createLegacyEvent(
ParsedCloudEvent event, CloudFunctionsContext.Builder builder, JsonObject data) {
JsonObject resource = new JsonObject();
resource.addProperty("service", event.Service);
resource.addProperty("name", event.Resource);
if (data.has("kind")) {
resource.addProperty("type", data.get("kind").getAsString());
}
builder.setResource(GSON.toJson(resource));
return Event.of(data, builder.build());
}