♻️ Favor Hyku::Application.path_for over Rails.root

Given the existence of Knapsack we need to consider how overrides in
Knapsack will take precedence over Hyku files.  This change handles
cases where we want to use the Knapsack's uploaded thumbnails.

Related to:

- #2010

app/services/uploaded_collection_thumbnail_path_service.rb

@@ -9,11 +9,11 @@ def call(object)
 
     # rubocop:disable Metrics/LineLength, Rails/FilePath, Lint/StringConversionInInterpolation
     def uploaded_thumbnail?(collection)
-      File.exist?("#{Rails.root.to_s}/public/uploads/uploaded_collection_thumbnails/#{collection.id}/#{collection.id}_card.jpg")
+      File.exist?(File.join(upload_dir(collection), "#{collection.id}_card.jpg"))
     end
 
     def upload_dir(collection)
-      "#{Rails.root.to_s}/public/uploads/uploaded_collection_thumbnails/#{collection.id}"
+      Hyku::Application.path_for("public/uploads/uploaded_collection_thumbnails/#{collection.id}")
     end
     # rubocop:enable Metrics/LineLength, Rails/FilePath, Lint/StringConversionInInterpolation
   end

app/views/hyrax/dashboard/collections/_current_thumbnail.html.erb

@@ -1,5 +1,5 @@
 <% thumbnail_path = SolrDocument.find(@collection.id).thumbnail_path %>
- <% if thumbnail_path.include?("uploaded_collection_thumbnails") and File.exist? Rails.root.join("public#{::SolrDocument.find(@collection.id).thumbnail_path}") %>
+ <% if thumbnail_path.include?("uploaded_collection_thumbnails") and File.exist? Hyky::Application.path_for("public#{::SolrDocument.find(@collection.id).thumbnail_path}") %>
   <%= image_tag(thumbnail_path, class: "current-thumbnail") %>
   <p>Current image: <strong><%= @thumbnail_filename %></strong></p>
 <% else %>