Update vacancies controller campaign action

Better to use `ActiveModel::Type::Boolean.new.cast(value)` to catch more
truthy values

app/controllers/vacancies_controller.rb

@@ -69,9 +69,9 @@ def campaign_search_params
       campaign_params[:subjects] = [campaign_params.delete(:email_subject)].compact
       campaign_params[:phases] = [campaign_params.delete(:email_phase)].compact
       working_patterns = []
-      working_patterns << "full_time" if campaign_params.delete(:email_fulltime) == "true"
-      working_patterns << "part_time" if campaign_params.delete(:email_parttime) == "true"
-      working_patterns << "job_share" if campaign_params.delete(:email_jobshare) == "true"
+      working_patterns << "full_time" if ActiveModel::Type::Boolean.new.cast(campaign_params.delete(:email_fulltime)) == "true"
+      working_patterns << "part_time" if ActiveModel::Type::Boolean.new.cast(campaign_params.delete(:email_parttime)) == "true"
+      working_patterns << "job_share" if ActiveModel::Type::Boolean.new.cast(campaign_params.delete(:email_jobshare)) == "true"
       campaign_params[:working_patterns] = working_patterns
       campaign_params[:ect_statuses] = [campaign_params.delete(:email_ECT)].compact
     end