[RESILIENCE] Request deduplication / idempotency keys — prevent duplicate writes on retry

[ElioNeto]

Description

When clients retry failed requests, they can create duplicate writes. Idempotency keys prevent this.

Implementation

1. Client sends Idempotency-Key: <UUID> header with PUT requests
2. ApexStore stores the idempotency key and its response for T seconds
3. If the same key arrives within the TTL, return the cached response instead of executing again
4. Cleanup expired keys periodically
5. Configuration:

resilience:
  idempotency:
    enabled: true
    ttl_secs: 86400  # 24h
    max_keys: 100000

Labels

[ElioNeto]

Implemented in commit 0871d91.