Add Cloudflare cache tag purging

[TorstenDittmann]

What changed

• map the provider-neutral purgeKeys() operation to Cloudflare cache-tag purges
• send cache tags to Cloudflare's /purge_cache endpoint in batches of 30
• document Cloudflare cache-tag usage and add request/batching coverage

Why

The cache abstraction exposed key purging for Fastly, but the Cloudflare adapter rejected the same operation even though Cloudflare supports equivalent cache-tag invalidation. This prevented proxy fan-out from invalidating tagged content on Cloudflare.

Impact

Consumers can now call Cache::purgeKeys() with their shared invalidation identifiers and purge both Fastly surrogate keys and Cloudflare cache tags without changing the public API.

Validation

• composer test — 26 tests, 49 assertions
• composer lint
• composer analyse

[greptile-apps]

Greptile Summary

The PR adds Cloudflare cache-tag invalidation to the provider-neutral purgeKeys() operation.

• Sends tag purge requests to Cloudflare’s zone-level purge_cache endpoint.
• Splits tag lists into batches of 30 and preserves empty-input behavior.
• Adds request-shape and batching tests and documents Cloudflare usage.

Confidence Score: 5/5

The PR appears safe to merge, with no concrete changed-code defect identified.

The implementation follows the existing Cloudflare purge request pattern, handles empty inputs, batches tags conservatively, checks provider success responses, and is covered for payload shape and batch boundaries.

Important Files Changed

Filename	Overview
src/Cdn/Cache/Adapter/Cloudflare.php	Replaces the unsupported-operation response with batched Cloudflare cache-tag purge requests using the adapter’s established request and error handling.
tests/Cdn/Cache/Adapter/CloudflareTest.php	Replaces the unsupported-operation test with coverage for tag payload construction and multi-request batching.
README.md	Documents Cloudflare cache-tag support through the existing provider-neutral key-purge API.

_{Reviews (1): Last reviewed commit: "Merge branch 'agent/cloudflare-cache-tag..." | Re-trigger Greptile}