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/builders/contact_builder_spec.rb

@@ -66,6 +66,20 @@ describe ::ContactBuilder do
       expect(contact_inbox.contact.id).to be(contact.id)
     end
 
+    it 'doesnot create contact when an uppercase email is passed for an already existing contact email' do
+      contact_inbox = described_class.new(
+        source_id: '123456',
+        inbox: inbox,
+        contact_attributes: {
+          name: 'Contact',
+          phone_number: '+1234567890',
+          email: contact.email.upcase
+        }
+      ).perform
+
+      expect(contact_inbox.contact.id).to be(contact.id)
+    end
+
     it 'doesnot create contact if it already exist with phone number' do
       contact_inbox = described_class.new(
         source_id: '123456',