Export CacheOverride API for cross-platform cache control

[trieloff]

Background

Per adobe/helix-deploy-plugin-edge#77 and comment, @adobe/fetch should export a CacheOverride API that provides cross-platform cache control for both Fastly Compute and Cloudflare Workers.

Proposal

Export a CacheOverride class/object that:

• On Fastly: Uses native fastly:cache-override module
• On Cloudflare: Maps to cf.cacheTtl, cf.cacheKey, cf.cacheTtlByStatus options

Common Options

• Mode: "none", "pass", "override"
• TTL: Time-to-live in seconds
• SWR: Stale-while-revalidate (Fastly only, graceful degradation on Cloudflare)
• Cache Key: Custom cache key string
• Surrogate Key: For cache purging (Fastly only, maps to cf.cacheTags on Cloudflare)

Usage

import { fetch, CacheOverride } from '@adobe/fetch';

const cacheOverride = new CacheOverride('override', { 
  ttl: 3600,
  swr: 86400 
});

const response = await fetch(url, { cacheOverride });

Platform Mapping

Feature	Fastly	Cloudflare
Mode: pass	cacheOverride mode	cf.cacheTtl: 0
TTL	ttl option	cf.cacheTtl
SWR	swr option	Not supported
Cache Key	cacheKey in CacheOverride	cf.cacheKey
Surrogate Key	surrogateKey option	cf.cacheTags