feat: Instagram reauthorization (#11221)

This PR is part of https://github.com/chatwoot/chatwoot/pull/11054 to
make the review cycle easier.

spec/mailers/administrator_notifications/channel_notifications_mailer_spec.rb

@@ -44,4 +44,18 @@ RSpec.describe AdministratorNotifications::ChannelNotificationsMailer do
       expect(mail.to).to eq([administrator.email])
     end
   end
+
+  describe 'instagram_disconnect' do
+    let!(:instagram_channel) { create(:channel_instagram, account: account) }
+    let!(:instagram_inbox) { create(:inbox, channel: instagram_channel, account: account) }
+    let(:mail) { described_class.with(account: account).instagram_disconnect(instagram_inbox).deliver_now }
+
+    it 'renders the subject' do
+      expect(mail.subject).to eq('Your Instagram connection has expired')
+    end
+
+    it 'renders the receiver email' do
+      expect(mail.to).to eq([administrator.email])
+    end
+  end
 end