Overriding Elementor Forms with Stripe client library and relaying payloads between browser and backend -- 2

We have a WordPress Elementor Forms based signup flow. Part of the flow needs to be overwritten in the browser through direct use of the Stripe client library, so that entering the information into stripe also fills the hidden parts of the Elementor Form for shipping address and Setup Intent ID. To start the Stripe client library, we need to make an API call to obtain a secret key, and at the end of the signup we need to make one last API call to submit the Elementor Form and Stripe information. Both of these API calls have a key that must be protected from the client, so it implies the existence of a cloud function that can inject the key and relay the response back for at least one the first API call. The last call could possibly be handled by WP Get API without an extra server.

Reference documentation (also contains the next two links):
https://support.careglp.com/support/solutions/articles/73000637180-patient-case-creation-endpoint

Reference code for Google Cloud functions, Stripe client library, and Elementor forms override:
https://github.com/carevalidate/careglp-payment-sample

Reference form questions to submit (GLP-1 Global Intake Form):
https://docs.google.com/spreadsheets/d/1EbyheBa_KYVbgskhWfmBrK_6XxGVAi_sSKtcCoCJ0Qo/edit?gid=0#gid=0