chore: "Channel::TwilioSms" to be unique on account_sid+phone_number (#4188)

"Twilio::IncomingMessageService" searches for the correct "Channel::TwilioSms"
by account_sid+phone_number.  If these values are duplicated then which record it
finds is indeterminate and may alternate between queries.

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

db/migrate/20220315204137_add_account_sid_unique_index_to_channel_twilio_sms.rb

@@ -0,0 +1,39 @@
+class AddAccountSidUniqueIndexToChannelTwilioSms < ActiveRecord::Migration[6.1]
+  def change
+    clear_possible_duplicates
+
+    has_duplicates = Channel::TwilioSms.select(:phone_number).group(:phone_number).having('count(*) > 1').exists?
+
+    if has_duplicates
+      raise <<~ERR.squish
+        ERROR: You have duplicate values for phone_number in "channel_twilio_sms".
+        This causes Twilio account lookup to behave unpredictably. Please eliminate the duplicates
+        and then re-run this migration.
+      ERR
+    end
+
+    remove_index :channel_twilio_sms, [:account_id, :phone_number], unique: true
+    add_index :channel_twilio_sms, :phone_number, unique: true
+    # since look ups are done via account_sid + phone_number, we need to add a unique index
+    add_index :channel_twilio_sms, [:account_sid, :phone_number], unique: true
+  end
+
+  def clear_possible_duplicates
+    # based on the look up in saas it seems like only the first inbox is used in case of duplicates,
+    # so lets try to clear our inboxes with out conversations
+    duplicate_phone_numbers = Channel::TwilioSms.select(:phone_number).group(:phone_number).having('count(*) > 1').collect(&:phone_number)
+    duplicate_phone_numbers.each do |phone_number|
+      # we are skipping the first inbox that was created
+      Channel::TwilioSms.where(phone_number: phone_number).drop(1).each do |channel|
+        inbox = channel.inbox
+        # skip inboxes with conversations
+        next if inbox.conversations.count.positive?
+
+        inbox.destroy
+      end
+    end
+
+    # clear the accounts created with twilio sandbox whatsapp number
+    # Channel::TwilioSms.where(phone_number: 'whatsapp:+14155238886').each { |channel| channel.inbox.destroy }
+  end
+end