robots.txt is a domain-level document and does not vary by session.
Keying the cache by (domain, sid) was both wasteful and incorrect —
it caused redundant fetches when the same domain was accessed by different sessions.
- Cache is now keyed by domain string only; all sessions share one entry
- Removed asyncio.Event inflight-deduplication mechanism (superseded by the prefetch approach added in the next commit)
- clear_cache() loses the `sid` parameter (breaking change); clearing a domain now evicts the single shared entry for all sessions
- Updated tests to reflect shared-cache semantics
Files: scrapling/spiders/robotstxt.py, tests/spiders/test_robotstxt.py
Karim shoair