Index admin_sets using the configured predicate

Fixes #2405.
Connected to #1461

app/search_builders/hyrax/admin_admin_set_member_search_builder.rb

@@ -17,7 +17,7 @@ def initialize(scope:, collection:)
     # include filters into the query to only include the admin_set members (regardless of status)
     def in_admin_set(solr_parameters)
       solr_parameters[:fq] ||= []
-      solr_parameters[:fq] << "{!term f=isPartOf_ssim}#{collection.id}"
+      solr_parameters[:fq] << "{!term f=#{Hyrax.config.admin_set_predicate.qname.last}_ssim}#{collection.id}"
     end
   end
 end

app/services/hyrax/admin_set_service.rb

@@ -26,7 +26,7 @@ def search_results(access)
     # @param [Symbol] access :read or :edit
     # @param join_field [String] how are we joining the admin_set ids (by default "isPartOf_ssim")
     # @return [Array<Hyrax::AdminSetService::SearchResultForWorkCount>] a list with document, then work and file count
-    def search_results_with_work_count(access, join_field: "isPartOf_ssim")
+    def search_results_with_work_count(access, join_field: "#{Hyrax.config.admin_set_predicate.qname.last}_ssim")
       admin_sets = search_results(access)
       ids = admin_sets.map(&:id).join(',')
       query = "{!terms f=#{join_field}}#{ids}"