Handle `membership` in ProjectFinder

The ProjectFinder supports the `non_public` parameter. This can be used to find
only projects the user is member of.

lib/api/helpers.rb

@@ -257,10 +257,6 @@ module API
     # project helpers
     def filter_projects(projects)
-      if params[:membership]
-        projects = projects.merge(current_user.authorized_projects)
-      end
-
       if params[:owned]
         projects = projects.merge(current_user.owned_projects)
       end

lib/api/projects.rb

@@ -68,7 +68,10 @@ module API
         end
         def present_projects(options = {})
-          projects = ProjectsFinder.new(current_user: current_user).execute
+          finder_params = {}
+          finder_params[:non_public] = true if params[:membership].present?
+
+          projects = ProjectsFinder.new(current_user: current_user, params: finder_params).execute
           projects = filter_projects(projects)
           projects = projects.with_statistics if params[:statistics]
           projects = projects.with_issues_enabled if params[:with_issues_enabled]