Cache Invalidation & TTL Strategy

[mftee]

Extend the CacheClient with a proper cache invalidation strategy, including support for tagged invalidation groups and configurable TTL policies per data type.

Requirements:

• Add the following methods to CacheClient:
  • set_with_tags(key: &str, value: &T, ttl: u64, tags: &[&str]) -> Result<()> — stores the value and also adds the key to a Redis set for each tag (tag:<name> → set of keys)
  • invalidate_by_tag(tag: &str) -> Result<usize> — deletes all keys associated with the tag and removes the tag set; returns the count of deleted keys
  • delete(key: &str) -> Result<()> — delete a single key
  • extend_ttl(key: &str, additional_seconds: u64) -> Result<()> — extend expiry of an existing key
  • get_ttl(key: &str) -> Result<Option<u64>> — return remaining TTL in seconds
• Define a CacheTtl constants module:

  pub mod cache_ttl {
      pub const VERIFICATION_RESULT: u64 = 3600;  // 1 hour
      pub const TRANSFER_HISTORY: u64 = 300;       // 5 minutes
      pub const HASH_HISTORY: u64 = 300;           // 5 minutes
  }

• Use tag document:<hash> for all cache entries related to a document hash so they can be bulk-invalidated

Acceptance Criteria:

• invalidate_by_tag deletes all keys tagged with the given tag in a single operation
• extend_ttl on a non-existent key is a no-op (does not create the key)
• Unit tests using a mock Redis (or an actual embedded Redis in tests)
• All existing call sites updated to use the new set_with_tags and the constants