[fix] adapter-netlify: encode UInt8Array response bodies as base64

[Xenonym]

If an endpoint returns a UInt8Array body (e.g. for binary content), the function handler will fail as a Netlify function response body needs to be either a string or base64 encoded.

Let's encode UInt8Array response bodies as base64 so that endpoints returning UInt8Arrays function properly with the Netlify adapter.

[changeset-bot]

🦋 Changeset detected

Latest commit: d1acf08

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

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Name	Type
@sveltejs/adapter-netlify	Patch

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[Egnus]

Hi team, since this has been merged into version 1.0.0-next.34 I am getting in my netlify server this:

{
  "errorType": "TypeError",
  "errorMessage": "The first argument must be of type string or an instance of Buffer, ArrayBuffer, or Array or an Array-like Object. Received undefined",
  "trace": [
  "TypeError [ERR_INVALID_ARG_TYPE]: The first argument must be of type string or an instance of Buffer, ArrayBuffer, or Array or an Array-like Object. Received undefined",
  "    at Function.from (buffer.js:330:9)",
  "    at Runtime.handler (/var/task/.netlify/functions-internal/__render.js:21073:18)"
  ]
}

The given line in the __render.jswas like this:

var SignInSection = create_ssr_component(($$result, $$props, $$bindings, slots) => {

I believe more people are going to start having this issue as well.
I had to lock my version to 1.0.0-next.33 to avoid this problem.
For a little bit of more context, the page fails to load when there is a redirect in the first load to another page (signIn), where I did an initial fetch and some promises during the load phase.
But if I put the correct expected path then the page is loaded without issues. In earlier versions than 34, there is a SSR redirect and the page goes directly to the Signin page without issues.

[JeanJPNM]

I will fix it as soon as I get home

[Xenonym]

@JeanJPNM there's already a fix #2682 :)