- Whereas Send is for fire-and-forget type of calls, new `call` and `acall` functions are for flows where you want to wait for the node to finish before doing something else
- Because we return regular python future objects (concurrent.futures.Future or asyncio.Future) all the python primitives for working with futures work, eg. wait, gather, etc
Replace hardcoded database saver class names with `cls` in
`from_conn_string` factory methods to improve subclassing support
## Changes
* Replaced direct class instantiations with `cls(conn)` in
`from_conn_string` classmethods across all database implementations
* Updated both synchronous and asynchronous variants for DuckDB,
PostgreSQL, and SQLite savers
## Why
This refactor makes the database saver classes more extensible by
following Python's convention of using `cls` in class methods. This
enables proper inheritance patterns where subclasses can reuse the
factory methods without needing to override them. Previously, the
hardcoded class names would always instantiate the parent class, even
when called from a subclass.
## Testing
The change is backward compatible and doesn't alter existing
functionality. All existing tests should continue to pass as this is
purely a structural refactoring that preserves the current behavior
while improving extensibility.
## Notes
This PR addresses follow up on comments from #2518 - AsyncPostgresSaver
didn't need to be fixed but many of the other DB saver classes did.
vbarda