feat(adapter-netlify)!: migrate to the modern Netlify Functions API

[serhalp]

The Netlify adapter now generates "v2" Netlify Functions, which uses modern standards (ESM, Request, Response) instead of the legacy "Lambda-compatible" or "v1" format. Under the hood, this greatly simplifies the adapter code and improves maintainability. See more details in this guide: https://developers.netlify.com/guides/migrating-to-the-modern-netlify-functions/.

Some key changes:

• The use of Request/Resonse eliminated the need for special header parsing, special multi-value handling header, base64 encoding of binary responses, and more.
• Configuration of function routing directly in code eliminated the need for _redirects file generation.
• As a bonus, this ^ lets us remove the limitation that users cannot specify redirects in netlify.toml.

BREAKING CHANGES:

• platform.context type changed to https://docs.netlify.com/build/functions/api/#netlify-specific-context-object

---

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[changeset-bot]

🦋 Changeset detected

Latest commit: 312d3bf

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@sveltejs/adapter-netlify	Major

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-kit-15203-svelte.vercel.app/

[teemingc]

Thank you, this is really nice! LGTM. Is there anything we can do to get this out of draft? Ideally, we'd release these breaking changes together with the fix for #1604

[serhalp]

@teemingc It's almost there! I just wanted to:

• do a bit of manual testing
• polish up the changeset(s)
• give a think to what we want for excludedPath (here's what we do for edge functions) — I think preferStatic: true means we just need /.netlify/* here.

I should have some time today.

btw I also have a PR stacked on this one that ports to the modern https://docs.netlify.com/build/frameworks/frameworks-api/, as discussed 😁. I'll open that up later too.

[serhalp]

btw if we're doing a major we could do this one too:

kit/packages/adapter-netlify/index.js

Line 113 in 99836bf

// TODO bump peer dep in next adapter major to simplify this