[#139] Send conversation emails (#442)

* [#139] Delayed emails for conversations

* Added the setex and get methods to Redis wrapper
* Set the priorities for the sidekiq queues
* Was not able to use mailhog for testing email in local, switched back to letter opener and added comments on using the SMTP settings
* Added after create hood in messages to queue the sending of mail after 2 minutes using sidekiq worker and also set the redis key for the conversation to avoid the email sending for every message
* Added the sidekiq worker to send the email and delete the conversation redis key
* Added the mailer and mail template
* mailer sends the last 10 messages along with the new messages from the time it was queued

* Send email only in development or if smtp config is set

* Send email only in development or if smtp config is set
* Set the SMTP_PORT in production variable

* Adding redis to circle CI

* Specs for the conversation email changes

* Added specs for conversation email sidekiq worker
* Added specs for conversation mailer
* Added specs in message model for the after create hook for notify email

* Send emails only when there is a reply from agent

* set development to use mailhog

* Adding comments for using letter opener

spec/workers/conversation_email_worker_spec.rb

@@ -0,0 +1,37 @@
+require 'rails_helper'
+
+Sidekiq::Testing.fake!
+RSpec.describe ConversationEmailWorker, type: :worker do
+  let(:perform_at) { (Time.zone.today + 6.hours).to_datetime }
+  let(:scheduled_job) { described_class.perform_at(perform_at, 1, Time.zone.now) }
+  let(:conversation) { build(:conversation, display_id: nil) }
+
+  describe 'testing ConversationEmailWorker' do
+    before do
+      conversation.save!
+      allow(Conversation).to receive(:find).and_return(conversation)
+      mailer = double
+      allow(ConversationMailer).to receive(:new_message).and_return(mailer)
+      allow(mailer).to receive(:deliver_later).and_return(true)
+    end
+
+    it 'worker jobs are enqueued in the mailers queue' do
+      described_class.perform_async
+      assert_equal :mailers, described_class.queue
+    end
+
+    it 'goes into the jobs array for testing environment' do
+      expect do
+        described_class.perform_async
+      end.to change(described_class.jobs, :size).by(1)
+      described_class.new.perform(1, Time.zone.now)
+    end
+
+    context 'with actions performed by the worker' do
+      it 'calls ConversationMailer' do
+        described_class.new.perform(1, Time.zone.now)
+        expect(ConversationMailer).to have_received(:new_message)
+      end
+    end
+  end
+end