Add serverActions.allowedForwardedHosts option

[shuding]

This new option specifies a list of host names that are considered safe, to accept as Server Action requests if they're different from the initial request origin. It can be very helpful when the hosted app has many layers of reverse proxies ahead.

Closes #57397.

[ijjk]

Tests Passed

[ijjk]

Stats from current PR

Default Build

General Overall increase ⚠️

	vercel/next.js canary	vercel/next.js shu/5b9a	Change
buildDuration	10.8s	10.7s	N/A
buildDurationCached	5.9s	6s	⚠️ +113ms
nodeModulesSize	175 MB	175 MB	⚠️ +14.4 kB
nextStartRea..uration (ms)	418ms	426ms	N/A

Client Bundles (main, webpack)

	vercel/next.js canary	vercel/next.js shu/5b9a	Change
199-HASH.js gzip	30 kB	30 kB	N/A
3f784ff6-HASH.js gzip	53.2 kB	53.2 kB	✓
494.HASH.js gzip	182 B	182 B	✓
framework-HASH.js gzip	45.5 kB	45.5 kB	✓
main-app-HASH.js gzip	254 B	251 B	N/A
main-HASH.js gzip	33.1 kB	33.1 kB	N/A
webpack-HASH.js gzip	1.75 kB	1.75 kB	N/A
Overall change	98.9 kB	98.9 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	vercel/next.js shu/5b9a	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	vercel/next.js shu/5b9a	Change
_app-HASH.js gzip	205 B	205 B	✓
_error-HASH.js gzip	182 B	181 B	N/A
amp-HASH.js gzip	505 B	507 B	N/A
css-HASH.js gzip	322 B	323 B	N/A
dynamic-HASH.js gzip	2.59 kB	2.59 kB	N/A
edge-ssr-HASH.js gzip	258 B	259 B	N/A
head-HASH.js gzip	348 B	347 B	N/A
hooks-HASH.js gzip	369 B	368 B	N/A
image-HASH.js gzip	4.38 kB	4.38 kB	N/A
index-HASH.js gzip	256 B	256 B	✓
link-HASH.js gzip	2.67 kB	2.67 kB	N/A
routerDirect..HASH.js gzip	318 B	318 B	✓
script-HASH.js gzip	384 B	383 B	N/A
withRouter-HASH.js gzip	319 B	320 B	N/A
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Overall change	885 B	885 B	✓

Client Build Manifests

	vercel/next.js canary	vercel/next.js shu/5b9a	Change
_buildManifest.js gzip	484 B	484 B	✓
Overall change	484 B	484 B	✓

Rendered Page Sizes

	vercel/next.js canary	vercel/next.js shu/5b9a	Change
index.html gzip	529 B	527 B	N/A
link.html gzip	541 B	542 B	N/A
withRouter.html gzip	524 B	521 B	N/A
Overall change	0 B	0 B	✓

Edge SSR bundle Size

	vercel/next.js canary	vercel/next.js shu/5b9a	Change
edge-ssr.js gzip	96.2 kB	96.2 kB	N/A
page.js gzip	140 kB	140 kB	N/A
Overall change	0 B	0 B	✓

Middleware size

	vercel/next.js canary	vercel/next.js shu/5b9a	Change
middleware-b..fest.js gzip	625 B	627 B	N/A
middleware-r..fest.js gzip	148 B	151 B	N/A
middleware.js gzip	24.8 kB	24.8 kB	N/A
edge-runtime..pack.js gzip	1.92 kB	1.92 kB	✓
Overall change	1.92 kB	1.92 kB	✓

Diff details

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Commit: 0586386

[vercel-spaces]

Notifying the following users due to files changed in this PR based on this repo's notify modifiers:

@timneutkens, @ijjk, @huozhi:

packages/next/src/server/config.ts