Use fullpage redirect for billing in embedded apps

[kirillplatonov]

What this PR does

The use of redirect_to in embedded apps causes an infinite redirect. We need to use fullpage_redirect_to method instead.

Checklist

Before submitting the PR, please consider if any of the following are needed:

• Update CHANGELOG.md if the changes would impact users
• Update README.md, if appropriate.
• Update any relevant pages in /docs, if necessary
• For security fixes, the Disclosure Policy must be followed.

[kirillplatonov]

cc @andyw8 @teddyhwang @nelsonwittwer

[andyw8]

Thanks for this contribution @kirillplatonov. We'll do some testing to verify it but it makes sense.

[kirillplatonov]

@andyw8 sounds good. Thanks for the review! Let me know if any changes are needed.

[klenotiw]

Hello, sorry for the delay on the review! I couldn't figure out how to reproduce the infinite redirect. Could you post some instructions? Thanks for your time!

[kirillplatonov]

Hi @klenotiw,
You can reproduce it using Shopify Hotwire Sample repo. We have a dedicated branch with turned on billing:
https://github.com/kirillplatonov/shopify-hotwire-sample/tree/billing

1. Clone the repo: https://github.com/kirillplatonov/shopify-hotwire-sample
2. Switch to billing branch
3. Follow steps from Quick start guide to set things up: https://github.com/kirillplatonov/shopify-hotwire-sample/tree/billing#quick-start

I hope it will be sufficient. Please let me know if you'll need more information.

[kirillplatonov]

@klenotiw any update on that?