Complete removal of the legacy consent KV persistence path #883

Summary

Complete the legacy consent_store removal described and closed in #666.

The current code still contains consent KV load/save/delete helpers and ConsentPipelineInput plumbing, but production EcContext construction passes ec_id: None and kv_store: None, so those operations are not used. On the Fastly EdgeZero path, a configured consent_store can still be opened as a fail-closed route dependency even though the opened store is not wired into consent load/save.

This leaves dead persistence code, misleading documentation/configuration, and a store availability dependency that does not provide the advertised consent continuity.

Proposed direction

Follow the decision already recorded in #666: request cookies/headers/geo are the live consent source, while EC identity lifecycle and withdrawal state live in the EC identity store. Remove the remaining separate consent-KV path rather than accidentally wiring its read-before-write behavior onto the request hot path.

If persisted consent continuity has become a product requirement since #666, stop and define that contract explicitly before implementation instead of preserving the current half-wired state.

Acceptance criteria

• Remove consent_store from active configuration, examples, manifests, and adapter route dependencies.
• Remove unused consent KV fields and branches from ConsentPipelineInput and build_consent_context.
• Remove crates/trusted-server-core/src/storage/kv_store.rs and tests when no live caller remains.
• EdgeZero consent-dependent routes no longer open an otherwise-unused consent KV store.
• Documentation clearly states the authoritative sources for live consent and withdrawal enforcement.
• Existing consent gating and EC tombstone behavior remain unchanged.
• Migration/config parsing behavior for deployments that still contain consent_store is documented and tested.

Relevant code

• crates/trusted-server-core/src/consent/mod.rs
• crates/trusted-server-core/src/consent_config.rs
• crates/trusted-server-core/src/storage/kv_store.rs
• crates/trusted-server-core/src/ec/mod.rs
• crates/trusted-server-adapter-fastly/src/app.rs