Configure Fastly and Cloudflare logging destinations #123

Description

Support manifest-driven Fastly logging endpoints and Cloudflare Logpush destinations.

The manifest already accepts per-adapter endpoint, level and echo_stdout; Fastly consumes its endpoint during initialization. Cloudflare logger initialization is a no-op, and this schema does not implement Logpush destination provisioning/configuration.

Steps to reproduce

1. Inspect manifest logging resolution and Fastly logger initialization.
2. Compare Cloudflare logging setup with the original Logpush destination requirement.

Expected behavior

Applications have a documented manifest workflow for the supported Fastly endpoint and Cloudflare destination integration.

Impact

Fastly has a usable runtime endpoint setting, while the Cloudflare destination portion still needs an implementation contract.

Proposed fix

Retain the existing Fastly support. Define how Cloudflare destination configuration maps to provider APIs/CLI resources, including validation and ownership, then implement or explicitly document a supported handoff.

Done when

• Existing Fastly endpoint configuration remains supported and documented.
• Cloudflare Logpush destination fields and behavior are defined and validated.
• Provider setup/update/unsupported behavior is explicit; configuration does not silently become a no-op.
• Examples and tests cover both provider mappings without committing credentials.

Related

• Parent: Complete portable request observability #118.
• Structured output: Provide consistent structured logs across adapters #119.
• Manifest logging schema
• Fastly logging configuration consumer
• Cloudflare logger initialization