Adding support for Injected Data with Soy/Closure

[lpellegr]

Closure Templates supports injected data, aka ij data:
https://github.com/google/closure-templates/blob/master/documentation/concepts/ij-data.md

Unfortunately, the current SoySauceViewsRenderer implementation provided by micronaut-views does not support custom ij data.

I would be happy to submit a PR but before going further I would like to get feedback from the maintainers regarding the changes.

Currently, SoySauceViewsRenderer retrieves the map returned in the request controller and set it as data in the SoySauce.Renderer renderer instance with setData:

micronaut-views/views-soy/src/main/java/io/micronaut/views/soy/SoySauceViewsRenderer.java

Line 134 in a028eed

renderer.setData(context);

My suggestion is to check if the Map returned by the request controller contains a key called ij. If so, the entry is removed and the value used as injected data (by simply appending entries to the existing ijOverlay Map). Here is a quick implementation overview:

final Object ijData = context.remove("ij");

if (ijData instanceof Map) {
    ijOverlay.putAll((Map<? extends String, ?>) ijData);
} else {
    LOG.warn("Skipping invalid ij value. Expected Map but got " + ijData.getClass());
}

What do you think about such a change? would you accept a PR?