[fixes] add missing "to" in no_membership_warning email and send emai…

…l only once

app/jobs/membership_warning_job.rb

@@ -3,7 +3,7 @@ class MembershipWarningJob < ActiveJob::Base
 
   def perform
     User.without_memberships.find_each do |user|
-      if user.created_at < 15.days.ago && user.no_membership_warning?
+      if user.created_at.to_date == 15.days.ago.to_date && user.no_membership_warning?
         OrganizationNotifier.no_membership_warning(user).deliver_now
       end
     end

app/mailers/organization_notifier.rb

@@ -53,6 +53,7 @@ def no_membership_warning(user)
     I18n.with_locale(user.locale) do
       mail(
         subject: "Do not forget to join a Timebank",
+        to: user.email
       )
     end
   end

spec/jobs/membership_warning_job.rb

@@ -3,7 +3,7 @@
   let!(:user) { Fabricate(:user) }
   let!(:member) { Fabricate(:member, organization: org, user: user) }
   let!(:user_with_no_memberships) { Fabricate(:user) }
-  let!(:user_with_no_memberships2) { Fabricate(:user, created_at: 16.days.ago) }
+  let!(:user_with_no_memberships2) { Fabricate(:user, created_at: 15.days.ago) }
 
   describe '#perform' do
     it "should send emails in user's locale" do