Add search method to polls

So far the method does not take questions nor answers into account.

This way we'll be able to search polls in the SDG Management section.

lib/tasks/consul.rake

@@ -6,6 +6,7 @@ namespace :consul do
 
   desc "Runs tasks needed to upgrade from 1.2.0 to 1.3.0"
   task "execute_release_1.3.0_tasks": [
-    "db:load_sdg"
+    "db:load_sdg",
+    "db:calculate_tsv"
   ]
 end

lib/tasks/db.rake

@@ -10,4 +10,9 @@ namespace :db do
     ApplicationLogger.new.info "Adding Sustainable Development Goals content"
     load(Rails.root.join("db", "sdg.rb"))
   end
+
+  desc "Calculates the TSV column for all polls"
+  task calculate_tsv: :environment do
+    Poll.find_each(&:calculate_tsvector)
+  end
 end