HiPay: Fix parse authorization string

Description
-------------------------
This commit fixes the parse authorization string when the first value is nil
also fixes a issue trying to get the payment_method.brand when the
payment method is not a credit card

Unit test
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Finished in 0.800901 seconds.

23 tests, 59 assertions, 0 failures, 0 errors, 0 pendings, 0 omissions, 0 notifications
100% passed

28.72 tests/s, 73.67 assertions/s

Remote test
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Finished in 9.141401 seconds.

1 tests, 6 assertions, 0 failures, 0 errors, 0 pendings, 0 omissions, 0 notifications
100% passed

0.11 tests/s, 0.66 assertions/s

Rubocop
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795 files inspected, no offenses detected

lib/active_merchant/billing/gateways/hi_pay.rb

@@ -41,11 +41,12 @@ def authorize(money, payment_method, options = {})
             response = r.process { tokenize(payment_method, options) }
             card_token = response.params['token']
           elsif payment_method.is_a?(String)
-            _transaction_ref, card_token, payment_product = payment_method.split('|')
+            _transaction_ref, card_token, payment_product = payment_method.split('|') if payment_method.split('|').size == 3
+            card_token, payment_product = payment_method.split('|') if payment_method.split('|').size == 2
           end
-
+          payment_product = payment_method.is_a?(CreditCard) ? payment_method.brand : payment_product&.downcase
           post = {
-            payment_product: payment_product&.downcase || PAYMENT_PRODUCT[payment_method.brand],
+            payment_product: payment_product,
             operation: options[:operation] || 'Authorization',
             cardtoken: card_token
           }
@@ -66,7 +67,8 @@ def store(payment_method, options = {})
       end
 
       def unstore(authorization, options = {})
-        _transaction_ref, card_token, _payment_product = authorization.split('|')
+        _transaction_ref, card_token, _payment_product = authorization.split('|') if authorization.split('|').size == 3
+        card_token, _payment_product = authorization.split('|') if authorization.split('|').size == 2
         commit('unstore', { card_token: card_token }, options, :delete)
       end
 
@@ -227,7 +229,7 @@ def authorization_from(action, response)
       end
 
       def authorization_string(*args)
-        args.join('|')
+        args.flatten.compact.reject(&:empty?).join('|')
       end
 
       def post_data(params)

test/unit/gateways/hi_pay_test.rb

@@ -146,6 +146,19 @@ def test_purchase_with_stored_pm
     end.respond_with(successful_capture_response)
   end
 
+  def test_authorization_string_with_nil_values
+    auth_string_nil_value_first = @gateway.send :authorization_string, [nil, '123456', 'visa']
+    assert_equal '123456|visa', auth_string_nil_value_first
+
+    auth_string_nil_values = @gateway.send :authorization_string, [nil, '123456', nil]
+    assert_equal '123456', auth_string_nil_values
+  end
+
+  def test_authorization_string_with_full_values
+    complete_auth_string = @gateway.send :authorization_string, %w(86786788 123456 visa)
+    assert_equal '86786788|123456|visa', complete_auth_string
+  end
+
   def test_purhcase_with_credit_card; end
 
   def test_capture