Fix for markdown viewer

ApplicationController#renderer initialization receives a Warden::Proxy
to avoid Devise errors.

app/presenters/snippet_blob_presenter.rb

 # frozen_string_literal: true
 
 class SnippetBlobPresenter < BlobPresenter
-  include Gitlab::Routing
-
   def rich_data
     return if blob.binary?
     return unless blob.rich_viewer
@@ -35,22 +33,16 @@ class SnippetBlobPresenter < BlobPresenter
   end
 
   def render_rich_partial
-    renderer.render("projects/blob/viewers/#{blob.rich_viewer.partial_name}",
-                    viewer: blob.rich_viewer,
-                    blob: blob,
-                    blow_raw_path: raw_path)
+    renderer.render("projects/blob/viewers/_#{blob.rich_viewer.partial_name}",
+                    locals: { viewer: blob.rich_viewer, blob: blob, blob_raw_path: raw_path },
+                    layout: false)
   end
 
   def renderer
-    ActionView::Base.new(build_lookup_context, { snippet: snippet }, ActionController::Base.new).tap do |renderer|
-      renderer.extend ApplicationController._helpers
-      renderer.class_eval do
-        include Rails.application.routes.url_helpers
-      end
+    proxy = Warden::Proxy.new({}, Warden::Manager.new({})).tap do |i|
+      i.set_user(current_user, scope: :user)
     end
-  end
 
-  def build_lookup_context
-    ActionView::Base.build_lookup_context(ActionController::Base.view_paths)
+    ApplicationController.renderer.new('warden' => proxy)
   end
 end