Braintree: Support override_application_id (#5194)

* Braintree: Support override_application_id

COMP-266

ActiveMerchant currently uses Class.application_id or @options[:channel] to let merchants
pass platform BN codes to gateways to signify that a transaction may be going to one merchant's
accounts but it originates from a platform or aggregator.

This poses a problem in that the Class value is assigned at compile time and the @options[:channel]
refers to a static value used when initializing the class.

This commit adds support for `override_application_id` which is a way for aggregators to pass in a
new BN code at transaction time alongside transaction parameters.

Test Summary
Remote:
123 tests, 661 assertions, 0 failures, 0 errors, 0 pendings, 0 omissions, 0 notifications
100% passed

Cannot add a remote test because there is no generic `channel` value

* drop unnecessary ensure

* simplify tests

* changelog

CHANGELOG

@@ -10,6 +10,7 @@
 * Elavon: Update sending CVV for MIT transactions  [almalee24] #5210
 * Adyen: Fix NT integration [jherreraa] #5155
 * HPS: Update NetworkTokenizationCreditCard flow [almalee24] #5178
+* Braintree: Support override_application_id [aenand] #5194
 
 == Version 1.137.0 (August 2, 2024)
 * Unlock dependency on `rexml` to allow fixing a CVE (#5181).

lib/active_merchant/billing/gateways/braintree_blue.rb

@@ -815,7 +815,7 @@ def add_addresses(parameters, options)
       end
 
       def add_channel(parameters, options)
-        channel = @options[:channel] || application_id
+        channel = options[:override_application_id] || @options[:channel] || application_id
         parameters[:channel] = channel if channel
       end
 

test/unit/gateways/braintree_blue_test.rb

@@ -939,7 +939,7 @@ def test_that_setting_a_wiredump_device_on_the_gateway_sets_the_braintree_logger
     end
   end
 
-  def test_solution_id_is_added_to_create_transaction_parameters
+  def test_channel_is_added_to_create_transaction_parameters
     assert_nil @gateway.send(:create_transaction_parameters, 100, credit_card('41111111111111111111'), {})[:channel]
     ActiveMerchant::Billing::BraintreeBlueGateway.application_id = 'ABC123'
     assert_equal @gateway.send(:create_transaction_parameters, 100, credit_card('41111111111111111111'), {})[:channel], 'ABC123'
@@ -950,6 +950,15 @@ def test_solution_id_is_added_to_create_transaction_parameters
     ActiveMerchant::Billing::BraintreeBlueGateway.application_id = nil
   end
 
+  def test_override_application_id_is_sent_to_channel
+    gateway = BraintreeBlueGateway.new(merchant_id: 'test', public_key: 'test', private_key: 'test', channel: 'overidden-channel')
+    gateway_response = gateway.send(:create_transaction_parameters, 100, credit_card('41111111111111111111'), {})
+    assert_equal gateway_response[:channel], 'overidden-channel'
+
+    gateway_response = gateway.send(:create_transaction_parameters, 100, credit_card('41111111111111111111'), { override_application_id: 'override-application-id' })
+    assert_equal gateway_response[:channel], 'override-application-id'
+  end
+
   def test_successful_purchase_with_descriptor
     Braintree::TransactionGateway.any_instance.expects(:sale).with do |params|
       (params[:descriptor][:name] == 'wow*productname') &&