Function assert_session_store_conformance 

pub async fn assert_session_store_conformance(
    store: &dyn SessionStore,
    record: SessionRecord,
)

Assert that a SessionStore implementation honors the trait contract.

Drives store through &dyn SessionStore and checks:

• save then load round-trips the record unchanged
• delete removes it, after which load returns StorageError::NotFound
• a second delete of the now-absent id still succeeds (idempotent)

record must use a session id the store does not already hold. Panics with a descriptive message on the first violated invariant.