♻️ Introduce Hyku::Application.theme_view_path_roots

With the introduction of [HykuKnapsack][1], we are adjusting how we
create instances of Hyku.  Namely we don't clone Hyku but instead we
incorporate Hyku as a submodule into a Knapsack.

The Knapsack is a Rails engine that is mounted in the Hyku application.
What this means is that when we want to

Prior to this commit, the only way to adjust themed views would have
been to add them to the Rails application (e.g. Hyku) directly.  Which
would work in a non-Knapsack ecosystem.

However, with Knapsack we need a means of saying "Hey, for themes we
want to be able to add/adjust views within the knapsack."  Hence this
change.

[1]: https://github.com/samvera-labs/hyku_knapsack

app/controllers/concerns/hyrax/works_controller_behavior.rb

@@ -505,8 +505,10 @@ def available_admin_sets
       def inject_show_theme_views
         if show_page_theme && show_page_theme != 'default_show'
           original_paths = view_paths
-          show_theme_view_path = Rails.root.join('app', 'views', "themes", show_page_theme.to_s)
-          prepend_view_path(show_theme_view_path)
+          Hyku::Application.theme_view_path_roots.each do |root|
+            show_theme_view_path = File.join('app', 'views', "themes", show_page_theme.to_s)
+            prepend_view_path(show_theme_view_path)
+          end
           yield
           # rubocop:disable Lint/UselessAssignment, Layout/SpaceAroundOperators, Style/RedundantParentheses
           # Do NOT change this line. This is calling the Rails view_paths=(paths) method and not a variable assignment.

app/controllers/hyrax/contact_form_controller.rb

@@ -102,8 +102,10 @@ def collections(rows: 6)
       def inject_theme_views
         if home_page_theme && home_page_theme != 'default_home'
           original_paths = view_paths
-          home_theme_view_path = Rails.root.join('app', 'views', "themes", home_page_theme.to_s)
-          prepend_view_path(home_theme_view_path)
+          Hyku::Application.theme_view_path_roots.each do |root|
+            home_theme_view_path = File.join(root, 'app', 'views', "themes", home_page_theme.to_s)
+            prepend_view_path(home_theme_view_path)
+          end
           yield
           # rubocop:disable Lint/UselessAssignment, Layout/SpaceAroundOperators, Style/RedundantParentheses
           # Do NOT change this line. This is calling the Rails view_paths=(paths) method and not a variable assignment.

app/controllers/hyrax/pages_controller.rb

@@ -101,8 +101,10 @@ def collections(rows: 6)
       def inject_theme_views
         if home_page_theme && home_page_theme != 'default_home'
           original_paths = view_paths
-          home_theme_view_path = Rails.root.join('app', 'views', "themes", home_page_theme.to_s)
-          prepend_view_path(home_theme_view_path)
+          Hyku::Application.theme_view_path_roots.each do |root|
+            home_theme_view_path = File.join(root, 'app', 'views', "themes", home_page_theme.to_s)
+            prepend_view_path(home_theme_view_path)
+          end
           yield
           # rubocop:disable Lint/UselessAssignment, Layout/SpaceAroundOperators, Style/RedundantParentheses
           # Do NOT change this method. This is an override of the view_paths= method and not a variable assignment.

config/application.rb

@@ -62,13 +62,30 @@ class Application < Rails::Application
     # IiifPrint::SplitPdfs::AdventistPagesToJpgsSplitter
     config.autoload_paths.unshift("#{Rails.root}/lib")
 
+    ##
+    #   @return [Array<String>] an array of strings in which we should be looking for theme view
+    #           candidates.
+    # @see Hyrax::WorksControllerBehavior
+    # @see Hyrax::ContactFormController
+    # @see Hyrax::PagesController
+    # @see https://api.rubyonrails.org/classes/ActionView/ViewPaths.html#method-i-prepend_view_path
+    #
+    # @see .path_for
+    # @see
+    def self.theme_view_path_roots
+      returning_value = [Rails.root.to_s]
+      returning_value.push HykuKnapsack::Engine.root.to_s if defined?(HykuKnapsack)
+      returning_value
+    end
+
     ##
     # @api public
     #
     # @param relative_path [String] lookup the relative paths first in the Knapsack then in Hyku.
     #
     # @return [String] the path to the file, favoring those found in the knapsack but falling back
     #         to those in the Rails.root.
+    # @see .theme_view_path_roots
     def self.path_for(relative_path)
       if defined?(HykuKnapsack)
         engine_path = HykuKnapsack::Engine.root.join(relative_path)