Nuvei: Add GSF for verify method

Description
-------------------------
[SER-1462](https://spreedly.atlassian.net/browse/SER-1462)

This commit add authenticationOnlyType as GSF for a verify request

Unit test
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Finished in 0.009788 seconds.

18 tests, 99 assertions, 0 failures, 0 errors, 0 pendings, 0 omissions, 0 notifications
100% passed

1838.99 tests/s, 10114.43 assertions/s

Remote test
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Finished in 121.496082 seconds.

28 tests, 87 assertions, 0 failures, 0 errors, 0 pendings, 0 omissions, 0 notifications
100% passed

0.23 tests/s, 0.72 assertions/s

Rubocop
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801 files inspected, no offenses detected

lib/active_merchant/billing/gateways/nuvei.rb

@@ -38,7 +38,7 @@ def authorize(money, payment, options = {}, transaction_type = 'Auth')
         add_customer_ip(post, options)
         add_stored_credentials(post, payment, options)
         post[:userTokenId] = options[:user_token_id] if options[:user_token_id]
-
+        post[:authenticationOnlyType] = options[:authentication_only_type] if options[:authentication_only_type]
         if options[:execute_threed]
           execute_3ds_flow(post, money, payment, transaction_type, options)
         else

test/remote/gateways/remote_nuvei_test.rb

@@ -191,6 +191,12 @@ def test_successful_verify
     assert_match 'APPROVED', response.message
   end
 
+  def test_successful_verify_with_authentication_only_type
+    response = @gateway.verify(@credit_card, @options.merge({ authentication_only_type: 'MAINTAINCARD' }))
+    assert_match 'SUCCESS', response.params['status']
+    assert_match 'APPROVED', response.message
+  end
+
   def test_successful_general_credit
     credit_response = @gateway.credit(@amount, @credit_card, @options)
     assert_success credit_response

test/unit/gateways/nuvei_test.rb

@@ -251,6 +251,20 @@ def test_successful_stored_credentials_merchant_recurring
     end.respond_with(successful_purchase_response)
   end
 
+  def test_successful_verify
+    @options.merge!(authentication_only_type: 'ACCOUNTVERIFICATION')
+    stub_comms(@gateway, :ssl_request) do
+      @gateway.verify(@credit_card, @options)
+    end.check_request(skip_response: true) do |_method, endpoint, data, _headers|
+      if /payment/.match?(endpoint)
+        json_data = JSON.parse(data)
+        assert_match(/Auth/, json_data['transactionType'])
+        assert_match(/ACCOUNTVERIFICATION/, json_data['authenticationOnlyType'])
+        assert_equal '0', json_data['amount']
+      end
+    end
+  end
+
   private
 
   def three_ds_assertions(payment_option_card)