Request Integration of Google Pay API

[Anid4u2c]

I've been working all day (and a few hours yesterday) on how to best implement the Google Pay Web API into my PWA. I was able to implement Google Authentication, using PolymerLabs/books/src/actions/auth.js as a template to authenticate a user.

Unlike the Google Pay API's new PaymentsClient(paymentOptions) method, the books implementation return is of type goog.Thenable. As such, I haven't been able to implement it using Redux... would the Polymer team consider adding this?

There is an older (working) integration build with Polymer 1.0, with no repo: https://polykart-credential-payment.appspot.com.

I did see this (closed) issue: #159 and subsequent comment... since online shopping is such a huge component of the web, it seems pertinent to implement Google's Pay API into the Shop's goals... especially since the API allows for testing (no credentials needed), and no additional dev dependencies.

[ncouture]

@Anid4u2c https://github.com/google-pay/shop-paydemo integrates Google Pay in Polymer shop 3.0.0.