Feature: Inbox greeting message (#927)

Co-authored-by: Pranav Raj S <pranav@thoughtwoot.com>

spec/mailboxes/conversation_mailbox_spec.rb

@@ -6,7 +6,7 @@ RSpec.describe ConversationMailbox, type: :mailbox do
   describe 'add mail as reply in a conversation' do
     let(:agent) { create(:user, email: 'agent1@example.com') }
     let(:reply_mail) { create_inbound_email_from_fixture('reply.eml') }
-    let(:conversation) { create(:conversation, assignee: agent) }
+    let(:conversation) { create(:conversation, assignee: agent, inbox: create(:inbox, greeting_enabled: false)) }
     let(:described_subject) { described_class.receive reply_mail }
     let(:serialized_attributes) { %w[text_content html_content number_of_attachments subject date to from in_reply_to cc bcc message_id] }