fix: undefined method contact in support mailbox (#2678)

if chatwoot receives an email of already existing contact with a different case say "Care@example.com", before this fix, it will throw an error. Now it will retrieve existing contact

Fixes: #2553


Co-authored-by: Sojan Jose <sojan@pepalo.com>

spec/presenters/mail_presenter_spec.rb

@@ -52,5 +52,9 @@ RSpec.describe MailPresenter do
       expect(data[:multipart]).to eq(true)
       expect(data[:subject]).to eq(decorated_mail.subject)
     end
+
+    it 'give email from in downcased format' do
+      expect(decorated_mail.from.first.eql?(mail.from.first.downcase)).to eq true
+    end
   end
 end