feat: Support Twilio Messaging Services (#4242)

This allows sending and receiving from multiple phone numbers using Twilio messaging services

Fixes: #4204

spec/factories/channel/twilio_sms.rb

@@ -2,11 +2,16 @@ FactoryBot.define do
   factory :channel_twilio_sms, class: 'Channel::TwilioSms' do
     auth_token { SecureRandom.uuid }
     account_sid { SecureRandom.uuid }
-    sequence(:phone_number) { |n| "+123456789#{n}1" }
+    messaging_service_sid { "MG#{Faker::Number.hexadecimal(digits: 32)}" }
     medium { :sms }
     account
     after(:build) do |channel|
       channel.inbox ||= create(:inbox, account: channel.account)
     end
+
+    trait :with_phone_number do
+      sequence(:phone_number) { |n| "+123456789#{n}1" }
+      messaging_service_sid { nil }
+    end
   end
 end