Make it possible to combine :trending with other params

Now it is possible to combine the :non_public parameter. This might be useful
when a user wants to know the trending projects they are member of.

app/finders/projects_finder.rb

@@ -32,6 +32,7 @@ class ProjectsFinder < UnionFinder
       item = by_ids(item)
       item = by_personal(item)
       item = by_starred(item)
+      item = by_trending(item)
       item = by_visibilty_level(item)
       item = by_tags(item)
       item = by_search(item)
@@ -46,12 +47,8 @@ class ProjectsFinder < UnionFinder
   def init_collection
     projects = []
 
-    if params[:trending].present?
-      projects << Project.trending
-    else
-      projects << current_user.authorized_projects if current_user
-      projects << Project.unscoped.public_to_user(current_user) unless params[:non_public].present?
-    end
+    projects << current_user.authorized_projects if current_user
+    projects << Project.unscoped.public_to_user(current_user) unless params[:non_public].present?
 
     projects
   end
@@ -72,6 +69,10 @@ class ProjectsFinder < UnionFinder
     (params[:starred].present? && current_user) ? items.starred_by(current_user) : items
   end
 
+  def by_trending(items)
+    params[:trending].present? ? items.trending : items
+  end
+
   def by_visibilty_level(items)
     params[:visibility_level].present? ? items.where(visibility_level: params[:visibility_level]) : items
   end