fix: Email attachments created with empty filename (#10420)

- We observed in prod for certain emails active storage blob objects
were getting created with empty file name. The conversations further
causes conversation and filter pages to break. This change will fix the
mentioned issue.

fixes:
https://linear.app/chatwoot/issue/CW-3331/missing-file-name-for-some-of-the-uploads-for-emails

---------

Co-authored-by: Pranav <pranavrajs@gmail.com>

spec/mailboxes/imap/imap_mailbox_spec.rb

@@ -43,6 +43,22 @@ RSpec.describe Imap::ImapMailbox do
       end
     end
 
+    context 'when the email has attachments with no filename' do
+      let(:inbound_mail) { create_inbound_email_from_fixture('attachments_without_filename.eml') }
+
+      it 'creates a conversation and a message with properly named attachments' do
+        expect do
+          class_instance.process(inbound_mail.mail, channel)
+        end.to change(Conversation, :count).by(1)
+
+        last_message = conversation.messages.last
+        expect(last_message.attachments.count).to be 2
+
+        filenames = last_message.attachments.map(&:file).map { |file| file.blob.filename.to_s }
+        expect(filenames.all? { |filename| filename.present? && filename.start_with?('attachment_') }).to be true
+      end
+    end
+
     context 'when the email has 15 or more attachments' do
       let(:inbound_mail) { create_inbound_email_from_fixture('multiple_attachments.eml') }