#21277: Fixed possible cache key collisions in output cache.

The cache keys of action method parameters are now prefixed with "PARAM:" to avoid collisions with built-in keys such as "theme". Similar to the "HEADER:" prefixing done for headers.

Work Item: 21277

src/Orchard.Web/Modules/Orchard.OutputCache/Filters/OutputCacheFilter.cs

@@ -334,7 +334,7 @@ namespace Orchard.OutputCache.Filters {
             
             // Vary by action parameters.
             foreach (var p in filterContext.ActionParameters)
-                result.Add(p.Key, p.Value);
+                result.Add("PARAM:" + p.Key, p.Value);
 
             // Vary by theme.
             result.Add("theme", _themeManager.GetRequestTheme(filterContext.RequestContext).Id.ToLowerInvariant());