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12.8 OnGooglePayLoaded()
This method creates a payments client, checks if Google Pay is ready, and sets up the payment gateway parameters.
In the tokenizationSpecification, use ‘exampleGatewayMerchantId’ until you go into production with your merchant id.
tokenizationSpecification = { type: 'PAYMENT_GATEWAY', parameters: { 'gateway': 'payway', 'gatewayMerchantId': 'exampleGatewayMerchantId' }