Enable phone/cc verification auto-swap for opt-in identity verification

What does this MR do and why?

Implements https://gitlab.com/gitlab-org/modelops/anti-abuse/team-tasks/-/issues/629?work_item_iid=655.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screen_Recording_2024-04-22_at_5.05.58_PM

How to set up and validate locally

1. Start GDK with SaaS simulation

   $ export GITLAB_SIMULATE_SAAS=1
   $ gdk start

2. Enable the relevant feature flags and configure required settings

   $ rails c
   > Feature.enable(:opt_in_identity_verification)
   > Feature.enable(:identity_verification_phone_number)
   > Feature.enable(:identity_verification_credit_card)
   > Feature.enable(:auto_request_phone_number_verification_exemption, type: :gitlab_com_derisk)

3. Setup Telesign

   $ rails c
   > ApplicationSetting.first.update(telesign_customer_xid: '<value_is_in_1Pass>', telesign_api_key: '<value_is_in_1Pass>')

   Credentials are in 1Password under Telesign API Keys (use GITLAB - DEVELOPMENT)

4. Update ee/lib/telesign/transaction_callback.rb to skip authentication of requests to /-/phone_verification/telesign_callback

   diff --git a/ee/lib/telesign/transaction_callback.rb b/ee/lib/telesign/transaction_callback.rb
   index 679ef54a23770..843c276183b1d 100644
   --- a/ee/lib/telesign/transaction_callback.rb
   +++ b/ee/lib/telesign/transaction_callback.rb
   @@ -14,6 +14,7 @@ def initialize(request, params)
        end
    
        def valid?
   +      return true
          return false unless signature.present?
    
          # https://developer.telesign.com/enterprise/docs/authenticate-callbacks

5. Login with root user

6. Go to http://localhost:3000/-/identity_verification

7. Send a code to a valid phone number

8. Update the reference id of the created phone number validation record

   $ rails c
   > User.first.phone_number_validation.update(telesign_reference_xid: '2557312299CC1304904080F4BE17BFB4')

9. Send a test callback request

   $ curl -X POST http://localhost:3000/-/phone_verification/telesign_callback -H 'Content-Type: application/json' -d '{ "status": { "updated_on": "2016-07-08T20:52:46.417428Z", "code": 237, "description": "Error delivering SMS to handset (reason unknown)" }, "errors": {}, "reference_id": "2557312299CC1304904080F4BE17BFB4" }'

10. Validate that "Phone number verification is unavailable at this time. Please verify with a credit card instead." info alert is displayed

11. Validate that Step 2: Verify phone number replaced with Step 2: Verify a payment method