Every record matching the query, ignoring pagination.
Exists so export can cover the whole result set rather than the current
page. Optional: a source over an unbounded remote collection may have no
safe way to honour it, and callers must degrade to list when absent.
Whether an operation was supplied, so callers can hide unavailable UI.
Adapts a bag of consumer-supplied functions to the full interface.
Exists so the rest of the library can depend on
CrudDataSourcewithout null-checking each method at every call site; absent operations fail here with a message naming what is missing.