Fix fetch_with_batched_keys to respect expires_in option for Redis TTL

[takehidemori]

Summary

Fix fetch_with_batched_keys to properly set Redis TTL when expires_in option is provided.

Problem

Currently, fetch_with_cache_register writes cache entries directly using redis.set without passing the ex: parameter, even when expires_in is specified. This causes Redis keys to persist indefinitely (TTL = -1), leading to memory growth in self-hosted environments.

The existing test passes because ActiveSupport::Cache::Entry stores expires_at internally and expiration is checked on the Ruby side during deserialization. However, Redis itself never evicts these keys.

Changes

• Pass ex: option to redis.set when expires_in is provided
• Add tests to verify Redis TTL is actually set

Testing

redis-cli TTL "cache_key_created_with_expires_in"
# Before: -1 (no expiration)
# After: 3600 (or whatever expires_in was set to)

Affected Areas

All ~40 call sites of fetch_with_batched_keys will now properly respect expires_in, including:

• user_learning_object_scopes.rb (already passes expires_in: but was ineffective)
• User, Course, Account caches
• Assignment overrides
• Role permissions
• And more