Python SDK: expose snapshot #4611

The Python SDK has no way to take a server snapshot. The Rust client and the C++ SDK both have one.

Where

• foreign/python/src/client.rs: a new snapshot method on the client.
• foreign/python/apache_iggy.pyi: the regenerated stub.
• foreign/python/tests/test_snapshot.py: a new test file.

Context

The Rust trait is SystemClient::snapshot(compression: SnapshotCompression, snapshot_types: Vec<SystemSnapshotType>) -> Result<Snapshot, IggyError> in core/common/src/traits/system_client.rs. Snapshot wraps a Vec<u8> (core/common/src/types/snapshot/mod.rs), so the Python method can return bytes with no new result class.

Both enums implement FromStr in that file, so the arguments can be plain strings, the way describe_options takes a scope string:

• compression: stored, deflated, bzip2, zstd, lzma, xz
• snapshot types: filesystem_overview, process_list, resource_usage, test, server_logs, server_config, all

The C++ SDK already does this in snapshot in foreign/cpp/src/client.rs, including rejecting an empty type list and an empty or unknown compression. Use it as the worked example.

Done looks like

• data = await client.snapshot("deflated", ["all"]) returns non-empty bytes against a real server.
• An unknown compression or snapshot type, or an empty type list, raises ValueError before any request is sent.
• The method has a docstring in the style of its neighbours, and the .pyi stub is regenerated.
• uv run --no-sync pytest tests/test_snapshot.py -v passes.

Steps

• Read snapshot in foreign/cpp/src/client.rs for the argument checks and the FromStr calls.
• Add snapshot(compression: &str, snapshot_types: Vec<String>) to foreign/python/src/client.rs, using future_into_py and to_runtime_error as get_stats does, and map bad input to PyValueError.
• Return the snapshot as bytes.
• Regenerate the stub with cargo run --bin stub_gen (see the Python README) and commit the apache_iggy.pyi change.
• Add test_snapshot.py modelled on test_stats.py: a happy path, an invalid compression, an empty type list, and "all" combined with another type (the C++ test SnapshotAllCombinedWithOtherTypeThrows shows the expected behaviour).