Points Hyrax::EditPermissionsService.build_service_object_from to Hyr…

…ax configuration variable.

For L#44, the `if` test's subject is hard-coded and unaware of any customized form class that the Hyrax Engine's implementers could create and set inside the Engine's configuration. This swaps to the configuration variable that defaults to the same hard-coded class (`Hyrax::Forms::FileSetForm`).

app/services/hyrax/edit_permissions_service.rb

@@ -41,7 +41,7 @@ def self.build_service_object_from(form:, ability:)
         # (+Hyrax::Forms::FileSetForm+), +:in_works_ids+ is prepopulated onto
         # the form object itself. For +Hyrax::Forms::FileSetEditForm+, the
         # +:in_works+ method is present on the wrapped +:model+.
-        if form.object.is_a?(Hyrax::Forms::FileSetForm)
+        if form.object.is_a?(Hyrax.config.file_set_form)
           object_id = form.object.in_works_ids.first
           new(object: Hyrax.query_service.find_by(id: object_id), ability: ability)
         else