add missing "X-Shopify-Triggered-At" in ShopifyHeader

[llong2195]

WHY are these changes introduced?

Fixes #0000

I read the documentation: https://shopify.dev/docs/apps/build/webhooks#key-terminology and found X-Shopify-Triggered-At missing

WHAT is this pull request doing?

This pull request adds the missing X-Shopify-Triggered-At header to the ShopifyHeader.

Type of change

• Patch: Bug (non-breaking change which fixes an issue)
• Minor: New feature (non-breaking change which adds functionality)
• Major: Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• I have used pnpm changeset to create a draft changelog entry (do NOT update the CHANGELOG.md files manually)
• I have added/updated tests for this change
• I have documented new APIs/updated the documentation for modified APIs (for public APIs)

[lizkenyon]

Hi there 👋

Thanks for your contribution!

I agree that we should have this header value.

I believe though for this value to be accessible we will need to modify the validate function to return this header value. Or are you using this in a different way?

[llong2195]

Currently I write my own verify webhook function, some needs need to get 'triggered-at' so I just add it in ShopifyHeader enum.

I agree that if someone needs it, it should also be edited a bit

[lizkenyon]

Thanks for the additional context! @llong2195

Would you be able to update a test for the validate function, to confirm this change?

Afterwards you will also need to add a changeset (pnpm changeset) as well as sign the CLA

[llong2195]

Thanks for the feedback! @lizkenyon
I tried but ran into too many issues and I don't understand enough to complete the tests. It seems the tests for webhooks are outdated.
Can you help me complete the rest?