Can't have different templates in multiple plugin instances hwne using USER_INT mode
When using user-int mode, one cannot have multiple plugins with different templates. This happens because the cache identifier depends solely on the feed URL, and the data saved in the cache is the result of template rendering, not the feed content.
1. (preferred) Keep cache identifier as is, but cache either the feed source code or the parsed feed. Caching of the rendered template should be done by fluid.
2. Add the content element uid to the cache identifier.
I prefer the first solution, since it prevents sending an HTTP request on each rendering, but leaves the caching of the output where it belongs. The second solution is only removing a symptom.