fix: Error shouldn't halt the campaign for entire audience (#11980)

## Summary
- handle Twilio failures per contact when running one-off SMS campaigns
- rescue errors in WhatsApp and generic SMS one-off campaigns so they
continue
- add specs confirming campaigns continue sending when a single contact
fails

fixes:  https://github.com/chatwoot/chatwoot/issues/9000

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>

spec/services/sms/oneoff_sms_campaign_service_spec.rb

@@ -20,6 +20,7 @@ describe Sms::OneoffSmsCampaignService do
         body: { 'id' => '1' }.to_json,
         headers: {}
       )
+      allow_any_instance_of(described_class).to receive(:channel).and_return(sms_channel) # rubocop:disable RSpec/AnyInstance
     end
 
     it 'raises error if the campaign is completed' do
@@ -52,5 +53,21 @@ describe Sms::OneoffSmsCampaignService do
 
       sms_campaign_service.perform
     end
+
+    it 'continues processing contacts when sending message raises an error' do
+      contact_error, contact_success = FactoryBot.create_list(:contact, 2, :with_phone_number, account: account)
+      contact_error.update_labels([label1.title])
+      contact_success.update_labels([label1.title])
+
+      error_message = 'SMS provider error'
+
+      expect(sms_channel).to receive(:send_text_message).with(contact_error.phone_number, anything).and_raise(StandardError, error_message)
+      expect(sms_channel).to receive(:send_text_message).with(contact_success.phone_number, anything).and_return(nil)
+
+      expect(Rails.logger).to receive(:error).with("[SMS Campaign #{campaign.id}] Failed to send to #{contact_error.phone_number}: #{error_message}")
+
+      sms_campaign_service.perform
+      expect(campaign.reload.completed?).to be true
+    end
   end
 end