skip mandatory webhook topics during registration/unregistration

[nelsonwittwer]

Description

Friction with mandatory webhooks was identified in the shopify app gem. Since Mandatory webhooks aren't subscribed to via API, we need to gracefully skip them during registrations without breaking handlers.

This skips registration/unregistration for mandatory topics that are managed in the partner dashboard

How has this been tested?

Unit tests within this library. I've also created a new app using our ruby app template pointing to this branch and my fix to the app gem's branch to verify I could recreate webhook without error.

Checklist:

• [x] My commit message follow the pattern described in here
• [x] I have performed a self-review of my own code.
• [x] I have added tests that prove my fix is effective or that my feature works.
• [x] I have updated the project documentation.
• [x] I have added a changelog line.

[mironov]

I think this breaks webhooks processing for mandatory webhooks.

https://github.com/Shopify/shopify-api-ruby/blob/82e4caf30c21a67a68384b5abcc897884dbc5065/lib/shopify_api/webhooks/registry.rb#L179-L183

The @registry[request.topic] will be nil for mandatory webhooks because they were skipped in https://github.com/Shopify/shopify-api-ruby/blob/82e4caf30c21a67a68384b5abcc897884dbc5065/lib/shopify_api/webhooks/registry.rb#L25-L27

[kirillplatonov]

Yep, I can confirm that too. Mandatory webhooks in v13.3.0 are broken. Please rollback this PR.

[nelsonwittwer]

Fixed with https://github.com/Shopify/shopify-api-ruby/pull/1249

[kirillplatonov]

Thanks for the quick fix! 🙏