🎁 Adds collection sorting by publication and creation date

This commit adds collection search options for sorting by ascending and descending publication dates and ascending and descending creation dates to the dropdown menu.

Ref:
- #650

app/controllers/catalog_controller.rb

@@ -22,6 +22,14 @@ def self.title_field
     'title_ssi'
   end
 
+  def self.published_field
+    'date_issued_d_ssi'
+  end
+
+  def self.created_field
+    'date_created_d_ssi'
+  end
+
   # CatalogController-scope behavior and configuration for BlacklightIiifSearch
   include BlacklightIiifSearch::Controller
 
@@ -396,6 +404,10 @@ def self.title_field
     config.add_sort_field "#{uploaded_field} asc", label: "date uploaded \u25B2"
     config.add_sort_field "#{modified_field} desc", label: "date modified \u25BC"
     config.add_sort_field "#{modified_field} asc", label: "date modified \u25B2"
+    config.add_sort_field "#{published_field} desc", label: "date published \u25BC"
+    config.add_sort_field "#{published_field} asc", label: "date published \u25B2"
+    config.add_sort_field "#{created_field} desc", label: "date created \u25BC"
+    config.add_sort_field "#{created_field} asc", label: "date created \u25B2"
 
     # OAI Config fields
     config.oai = {

app/indexers/collection_indexer.rb

@@ -13,6 +13,8 @@ def generate_solr_document
       solr_doc["bulkrax_identifier_sim"] = object.bulkrax_identifier
       solr_doc["account_cname_tesim"] = Site.instance&.account&.cname
       solr_doc[CatalogController.title_field] = object.title.first
+      solr_doc[CatalogController.published_field] = object.date_issued_d
+      solr_doc[CatalogController.created_field] = object.date_created_d
     end
   end