Add export_files

lib/tasks/collections.rake

@@ -2,6 +2,28 @@ require 'rake'
 
 namespace :collections do
 
+  desc "Export all files in a collection as a zip file"
+  task :export_files, [:collection_id, :dest_key] => :environment do |task, args|
+    collection      = Collection.find(args[:collection_id])
+    request_context = RequestContext.new(institution: collection.institution)
+    collection_ids  = [collection.id] + collection.all_child_ids
+
+    puts "Compiling a list of item IDs"
+    item_ids = []
+    relation = Item.search.filter(Item::IndexFields::COLLECTIONS, collection_ids)
+    ItemPolicy::Scope.new(request_context, relation).resolve.each_id_in_batches do |result|
+      item_ids << result[:id]
+    end
+
+    puts "Creating zip file"
+    Item.create_zip_file(item_ids:         item_ids,
+                         metadata_profile: collection.effective_metadata_profile,
+                         dest_key:         dest_key,
+                         include_csv_file: false,
+                         request_context:  request_context,
+                         print_progress:   true)
+  end
+
   desc "Reindex all collections"
   task reindex: :environment do
     # N.B.: orphaned documents are not deleted.