feat(vercel, netlify): introduce isr route rule

[pi0]

🔗 Linked issue

Resolves #946

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

We had been experimenting vercel ISR and netlify Builders feature via an implicit cache route rule.

Introducing a new isr flag, unblocks to combine nitro native cache (SWR) with platform native rules and giving the flexibility to use the most effective caching mechanism. (Currently, on these platforms nitro cache/storage cannot be used)

Note: This is a semi-breaking change for this platforms however switching swr to built-in behavior still preserves in memory cache so caching keeps working only can be changed to either isr or permanent by mounting /storage for production.

This PR also drops (almost unused) static cache rule.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[codecov]

Codecov Report

Merging #1124 (d3729e3) into main (ea5ea88) will decrease coverage by 0.04%.
The diff coverage is 94.11%.

@@            Coverage Diff             @@
##             main    #1124      +/-   ##
==========================================
- Coverage   67.77%   67.73%   -0.04%     
==========================================
  Files          63       63              
  Lines        6370     6345      -25     
  Branches      713      704       -9     
==========================================
- Hits         4317     4298      -19     
+ Misses       2039     2033       -6     
  Partials       14       14              

Impacted Files	Coverage Δ
src/options.ts	87.36% <ø> (-0.17%)	⬇️
src/presets/vercel.ts	77.72% <92.30%> (+0.93%)	⬆️
src/presets/netlify.ts	59.62% <100.00%> (-0.98%)	⬇️
src/types/nitro.ts	100.00% <100.00%> (ø)

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[danielroe]

This is 👌 A good implementation and addresses my worry about being too provider-specific.

But maybe worth (if not using vercel/netlify) setting native nitro cache options if isr is enabled?

[pi0]

But maybe worth (if not using vercel/netlify) setting native nitro cache options if isr is enabled?

It would be indeed a nice idea if we could emulate isr functionality for other production platforms. Let's iterate over this. I think one main difference that swr lacks is to invalidate/segment cache based on deployment id.

Feel free to make PR for both ideas btw.

[Hebilicious]

It should be possible to implement ISR for the cloudflare providers by leveraging the Cloudflare cache API like here. The isr value can be forwarded to the cache-control header as well.
This would be very neat 👌