In checkout page when we click Next button from shipping step, we can see a response named shipping-information that contains payment methods and totals information. Where is this response come and can i access/modify the response?
You need to modify following class
saveAddressInformation Method return payment info and total.
You can modify this class using plugin.
This is a response from Checkout Web API entry point:
/V1/guest-carts/:cartId/shipping-information - GuestShippingInformationManagementInterface::saveAddressInformation for guest customer
/V1/carts/mine/shipping-information - ShippingInformationManagementInterface::saveAddressInformation for logged customer.
/V1/carts/:cartId/shipping-information - ShippingInformationManagementInterface::saveAddressInformation for logged customer.
All Checkout Web API entry points are specified in webapi.xml.
To customize this response, you need to create own Web API services and override Checkout entry points in your custom
webapi.xml or use plugins for API interfaces implementations, but you must be sure what you won't broke Magento Checkout js components.