REST i18n resources are generally derived from static information inside plugins and are unlikely to change very often. We should use our short-term public caching headers for them instead of not specifying any caching headers.

That is, we need to change these lines:

httpContext.getResponse().setHeader("Cache-Control", "");
httpContext.getResponse().setHeader("Pragma", "");
httpContext.getResponse().setHeader("Expires", "");

to this:

CachingHeaders.PUBLIC_SHORT_TERM.apply(httpContext.getResponse());

In addition, we should probably configure the REST caching consistently in our central caching filter, rather than having custom handling in the plugin.