[FSSDK-12028] use save time for event expiration in event store

[raju-opti]

Summary

• Instead of saving an expiresAt time in event store, save the storedAt time instead. This will allow expiring event early which was save with a larger ttl before.

Test plan

Issues

• FSSDK-12028

[Copilot]

Pull Request Overview

This PR refactors the event storage mechanism to save the storedAt timestamp and ttl separately instead of a computed expiresAt timestamp. This enables dynamic event expiration based on the current store's TTL configuration rather than the TTL at the time of storage.

Key Changes:

• Changed StoredEvent type from storing expiresAt to storing _time object with storedAt and ttl fields
• Updated expiration logic to calculate expiration dynamically using current store TTL
• Maintained backward compatibility by handling events without time information

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
lib/event_processor/event_store.ts	Refactored StoredEvent type and updated set() and processStoredEvent() methods to use new time structure with dynamic TTL-based expiration
lib/event_processor/event_store.spec.ts	Updated test names, variable names, and assertions to validate new time-based storage structure

Comments suppressed due to low confidence (1)

lib/event_processor/event_store.spec.ts:211

• Avoid automated semicolon insertion (93% of all statements in the enclosing function have an explicit semicolon).

    }

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[coveralls]

coverage: 78.231%. remained the same
when pulling 37b82c3 on raju/event_created_at
into 4b35644 on master.