Identity on Spin, the same scope as T8 #1589

Summary

Identity on Spin, the same scope as T8; port the config block_on removal from RC commit 933de5921.

Part of #1558, server-side identity on every adapter. Plan ID T9, planned in wave 17 (after the MVP: Spin); priority P3, size L. Design: spec; order and dependencies: plan.

Requirements

ID-1 One EC lifecycle

On every supported adapter a consented document navigation or EC route call (ID-9) mints the EC, creates the record and sets ts-ec together. A cookie is never issued without a record. An existing EC is kept when geo is unknown.

ID-2 One shared record store

The identity logic stays in core and becomes awaitable (#1526). It runs on one EcKvStore over EdgeZero's KvStore (DEC-3). A store that cannot meet the contract makes startup reject identity configuration with a clear error.

ID-3 Partner APIs answered locally

Identify, batch sync, pull sync and admin lookup run on every adapter with a record store. Without one, identify and batch sync return a local error and never reach the publisher origin. Admin lookup already answers 501 locally; pull sync is outbound only.

ID-5 After-response work

Only pull sync and guarded follow-up writes run after the response is sent: after send on Fastly, a task drained on SIGTERM on Axum, waitUntil on Cloudflare. On Spin the work runs before the response (DEC-14; DEC-16 rules out skipping it).

ID-8 Body EIDs keep being saved

EIDs sent in the /auction body are saved to the record.

WB-1 Document and EC route responses only

Identity cookies are set on top-level HTML document responses and on EC route responses (ID-9), on every supported adapter.

SH-1 Built once

Settings, the partner registry, store clients and the HTTP client are built once per process or isolate.

SH-3 No executor nesting

No block_on runs inside async code.

SH-5 One app for every adapter

The identity routes (identify, batch sync, admin lookup and the EC route), pull sync, the EC lifecycle, provider lookups and cookie write-back run from one app built in core, which every adapter mounts and which builds its state once (SH-1). An adapter crate supplies only platform services: through EdgeZero where it offers them, and otherwise through the adapter's existing platform bridge until the EdgeZero ask lands (today Fastly's limiter, ID-6, and Fastly's geo, EZI-4). A capability an adapter lacks is an EdgeZero ask, never new code in that adapter (DEC-16).

Current state

What the code does today, from the design's survey at the revisions it names:

• ID-8: main saves them on Fastly; the provider stack and the RC's Axum lifecycle do not.
• WB-1: main mints ts-ec on Fastly navigations, and the RC adds Axum.
• SH-1: Cloudflare and Spin rebuild app state per request; Axum builds the partner registry per request (app.rs:495 at Cut Trusted Server over to EdgeZero PR 275 #1506's head 9ec4711d3) and the HTTP client per request on purpose, because a pooled client regressed a Next.js flow (main platform.rs:620-623). Keep that client choice unless a measurement shows the regression gone.
• SH-3: Make shared EC persistence awaitable #1526 wraps finalize in block_on (Fastly main.rs:550) and Collect server-side identity provider EIDs in a single page-load write #1487 calls block_on inside finalize (main.rs:699), which panic together. Core pull sync and Cloudflare and Spin config reads also call block_on on main; Make shared EC persistence awaitable #1526, Cut Trusted Server over to EdgeZero PR 275 #1506 and the RC remove the pull-sync one, RC commit 933de5921 removes Spin's, and Cloudflare's remains everywhere.
• SH-5: at Cut Trusted Server over to EdgeZero PR 275 #1506's head only the Fastly adapter wires identity (EC generation and finalization are called from its app.rs and main.rs); Axum, Cloudflare and Spin each build their own router without it.

Acceptance criteria

• ID-1: The conformance suite (T5) asserts on each supported adapter that a consented navigation creates the record and sets ts-ec in the same response, that a store failure sets no ts-ec, and that an existing EC survives unknown geo
• ID-1: On an unsupported adapter, startup with identity configuration fails
• ID-2: No adapter crate's non-test code implements EcKvStore, and a store reporting KvError::Unsupported for the contract fails startup with identity enabled
• ID-3: In each adapter's tests a capturing origin receives no identify or batch-sync request
• ID-3: With a store they run, without one they return 501
• ID-5: On Fastly, Axum and Cloudflare a follow-up write recorded after send is in the record before the next navigation, and on Axum SIGTERM waits for it (A3). On Spin the follow-up write lands before the response
• ID-8: On each supported adapter a body EID is in the record after the request
• WB-1: Identity Set-Cookie headers appear on navigation and EC route responses and never on asset or other API responses
• SH-1: An adapter test shows settings, the partner registry and store clients built once across two requests, and the HTTP client too, except Axum's, which stays per request until a measurement shows the Next.js regression gone
• SH-1: After that measurement Axum's client is held to the same rule
• SH-3: The remaining block_on calls are only at adapter entry points
• SH-5: No adapter crate's non-test code calls EC generation, finalization or an identity handler directly, and the same conformance suite (T5) runs on each supported adapter

Dependencies

Blocked by:

• Identity on Cloudflare through T21's shared app with EZI-2c's store, passing T5's suite #1588 Identity on Cloudflare through T21's shared app with EZI-2c's store, passing T5's suite (new in this plan)
• Integration-branch tag with the Spin parts edgezero#493 Integration-branch tag with the Spin parts (new in this plan)

Waits on these decisions:

• DEC-8 Cloudflare and Spin store (open). Which store Cloudflare and Spin use by default for the record: the DynamoDB or celld adapter, or a native store that meets the contract, per Platform support. Blocks EZI-2c, EZI-2s, R3, T8 and T9.
• DEC-14 Spin after-response work (open). The work runs before the response, because DEC-16 rules out skipping it. Open: the latency it may add and its bound. Blocks T9.

Blocks:

• Identity features pass on Spin, the same scope as T17 #1597 Identity features pass on Spin, the same scope as T17 (new in this plan)

Notes from the plan

• The Cloudflare and Spin tickets (T8, T9, T17, T18, the EZI c and s tickets, R3, R4, Cloudflare ClientInfo edgezero#91, As a developer I want to access client metadata in handlers edgezero#89 and "Blocked by" is set as a GitHub dependency between issues.