Add rake to move external_url to description

This rake move this field for Proposals and Legislation proposals.

lib/tasks/proposals.rake

@@ -0,0 +1,23 @@
+namespace :proposals do
+
+  desc "Move external_url to description"
+  task move_external_url_to_description: :environment do
+    include ActionView::Helpers::SanitizeHelper
+    include TextWithLinksHelper
+
+    models = [Proposal, Legislation::Proposal]
+
+    models.each do |model|
+      print "Move external_url to description for #{model}s"
+      model.find_each do |resource|
+        if resource.external_url.present?
+          resource.update_columns(description: "#{resource.description} "\
+                                  "<p>#{text_with_links(resource.external_url)}</p>",
+                                  external_url: "")
+          print "."
+        end
+      end
+      puts " ✅ "
+    end
+  end
+end