KvStore record contract with listing strong within a partition #472

Summary

KvStore record contract with listing strong within a partition, the Fastly provider and the local persistent store (PersistentKvStore).

Behavior

KvStore gains a read that returns a generation marker, writes in Add, Overwrite and IfGenerationMatch modes with a precondition-failed outcome, strongly consistent existence, and prefix listing that is strongly consistent within a partition: the caller declares how a key maps to its partition, and a listing whose prefix is a whole partition reads strongly. A store that cannot meet this reports KvError::Unsupported.

Acceptance criteria

• An EdgeZero contract suite passes against the Fastly provider under Viceroy and against EdgeZero's local persistent store (PersistentKvStore), which the Axum development server uses

Dependencies

Blocked by:

• PR feat: implement portable outbound HTTP and request lifecycle contracts #275 feat: implement portable outbound HTTP and request lifecycle contracts

Blocks:

• EZI-2b DynamoDB and celld providers on Axum meet the record contract (new in this plan)
• EZI-2c Cloudflare record store: portable providers and Workers KV pass the record contract (new in this plan)
• EZI-2s Spin record store: portable providers and Spin KV pass the record contract (new in this plan)
• R1b Integration-branch tag with the record contract: EZI-2a and EZI-2b (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 2 (MVP: Fastly and Axum); priority P1, size L.
• Requirement EZI-2a in the design.