After-response work on Cloudflare (waitUntil) #478

Summary

After-response work on Cloudflare (waitUntil).

Behavior

A task registered during a request runs after the response is delivered, bounded in time.

Acceptance criteria

• On Fastly and Axum the task runs after delivery, and on Axum SIGTERM waits for registered tasks up to the grace
• Later, on Cloudflare the task runs after delivery, and Spin returns a capability error

Dependencies

Blocked by:

• Bounded work after the response on Fastly and Axum, drained on Axum SIGTERM #476 Bounded work after the response on Fastly and Axum, drained on Axum SIGTERM (new in this plan)

Blocks:

• Integration-branch tag with the Cloudflare parts #492 Integration-branch tag with the Cloudflare parts (new in this plan)

Related

• Needed by Server-side identity on every adapter trusted-server#1558, server-side identity on every adapter. Planned in wave 10 (after the MVP: Cloudflare); priority P2, size S.
• Requirement EZI-1 in the design.