bug: Fields truncated when submitting form using Server Actions

[TryingToImprove]

When using Server Actions with a form the fields are getting truncated at 1MB because of busboy's default fieldSize limit of 1MB.

This PR tries to solve #59277 however there is a mismatch about fieldSize and bodySize. I have tried creating a PR for busboy mscdex/busboy#351 to allow configuring a max size for the entire body.

TODO:

• Figure out if this is acceptable
• Throw error when bodySizeLimit is hit.

Fixes #59277, closes #61462.

[TryingToImprove]

Unsure what to do here since busboy is pr. field whereas next is for the whole body.

[shuding]

How about the 3mb one?

[TryingToImprove]

When clicking the 3mb I think it said size = 2097152 since it is truncating the payload..

I guess it should throw instead, but busboy does not support that.

[ijjk]

Stats from current PR

Default Build (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	TryingToImprove/next.js fields-truncated-when-submitting-form	Change
buildDuration	13.8s	13.6s	N/A
buildDurationCached	7.3s	6.1s	N/A
nodeModulesSize	198 MB	198 MB	⚠️ +8.77 kB
nextStartRea..uration (ms)	429ms	434ms	N/A

Client Bundles (main, webpack)

	vercel/next.js canary	TryingToImprove/next.js fields-truncated-when-submitting-form	Change
2453-HASH.js gzip	30.5 kB	30.5 kB	N/A
3304.HASH.js gzip	181 B	181 B	✓
3f784ff6-HASH.js gzip	53.7 kB	53.7 kB	N/A
8299-HASH.js gzip	5.04 kB	5.04 kB	N/A
framework-HASH.js gzip	45.2 kB	45.2 kB	✓
main-app-HASH.js gzip	242 B	241 B	N/A
main-HASH.js gzip	32.2 kB	32.2 kB	N/A
webpack-HASH.js gzip	1.68 kB	1.68 kB	N/A
Overall change	45.4 kB	45.4 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	TryingToImprove/next.js fields-truncated-when-submitting-form	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	TryingToImprove/next.js fields-truncated-when-submitting-form	Change
_app-HASH.js gzip	196 B	197 B	N/A
_error-HASH.js gzip	184 B	184 B	✓
amp-HASH.js gzip	505 B	505 B	✓
css-HASH.js gzip	324 B	325 B	N/A
dynamic-HASH.js gzip	2.5 kB	2.5 kB	N/A
edge-ssr-HASH.js gzip	258 B	258 B	✓
head-HASH.js gzip	352 B	352 B	✓
hooks-HASH.js gzip	370 B	371 B	N/A
image-HASH.js gzip	4.21 kB	4.21 kB	✓
index-HASH.js gzip	259 B	259 B	✓
link-HASH.js gzip	2.67 kB	2.67 kB	N/A
routerDirect..HASH.js gzip	314 B	312 B	N/A
script-HASH.js gzip	386 B	386 B	✓
withRouter-HASH.js gzip	309 B	309 B	✓
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Overall change	6.57 kB	6.57 kB	✓

Client Build Manifests

	vercel/next.js canary	TryingToImprove/next.js fields-truncated-when-submitting-form	Change
_buildManifest.js gzip	481 B	484 B	N/A
Overall change	0 B	0 B	✓

Rendered Page Sizes

	vercel/next.js canary	TryingToImprove/next.js fields-truncated-when-submitting-form	Change
index.html gzip	529 B	528 B	N/A
link.html gzip	540 B	541 B	N/A
withRouter.html gzip	523 B	523 B	✓
Overall change	523 B	523 B	✓

Edge SSR bundle Size

	vercel/next.js canary	TryingToImprove/next.js fields-truncated-when-submitting-form	Change
edge-ssr.js gzip	95.1 kB	95.1 kB	N/A
page.js gzip	3.05 kB	3.05 kB	N/A
Overall change	0 B	0 B	✓

Middleware size

	vercel/next.js canary	TryingToImprove/next.js fields-truncated-when-submitting-form	Change
middleware-b..fest.js gzip	624 B	625 B	N/A
middleware-r..fest.js gzip	151 B	151 B	✓
middleware.js gzip	25.5 kB	25.5 kB	N/A
edge-runtime..pack.js gzip	839 B	839 B	✓
Overall change	990 B	990 B	✓

Next Runtimes

	vercel/next.js canary	TryingToImprove/next.js fields-truncated-when-submitting-form	Change
app-page-exp...dev.js gzip	171 kB	171 kB	N/A
app-page-exp..prod.js gzip	96.6 kB	96.6 kB	N/A
app-page-tur..prod.js gzip	98.3 kB	98.3 kB	N/A
app-page-tur..prod.js gzip	92.8 kB	92.8 kB	N/A
app-page.run...dev.js gzip	149 kB	149 kB	N/A
app-page.run..prod.js gzip	91.3 kB	91.3 kB	N/A
app-route-ex...dev.js gzip	21.3 kB	21.3 kB	✓
app-route-ex..prod.js gzip	15 kB	15 kB	✓
app-route-tu..prod.js gzip	15 kB	15 kB	✓
app-route-tu..prod.js gzip	14.8 kB	14.8 kB	✓
app-route.ru...dev.js gzip	21 kB	21 kB	✓
app-route.ru..prod.js gzip	14.8 kB	14.8 kB	✓
pages-api-tu..prod.js gzip	9.52 kB	9.52 kB	✓
pages-api.ru...dev.js gzip	9.8 kB	9.8 kB	✓
pages-api.ru..prod.js gzip	9.52 kB	9.52 kB	✓
pages-turbo...prod.js gzip	22.3 kB	22.3 kB	✓
pages.runtim...dev.js gzip	22.9 kB	22.9 kB	✓
pages.runtim..prod.js gzip	22.3 kB	22.3 kB	✓
server.runti..prod.js gzip	50.6 kB	50.6 kB	✓
Overall change	249 kB	249 kB	✓

build cache Overall increase ⚠️

	vercel/next.js canary	TryingToImprove/next.js fields-truncated-when-submitting-form	Change
0.pack gzip	1.56 MB	1.56 MB	N/A
index.pack gzip	105 kB	105 kB	⚠️ +109 B
Overall change	105 kB	105 kB	⚠️ +109 B

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Commit: b8f2c11