Python Library

Building on #2615, this PR updates the Python library bindings. This PR does not include:

• PerspectiveWidget support PerspectiveWidget support for new Python API #2658
• pyodide build support New API pyodide sypport #2660 .
• Windows, OSX, or Python versions other than 2.9 (pending).

Breaking API changes:

• date and datetime are not supported by the Table constructor anymore. These are not valid JSON values and JSON parsing is now language-agnostic. A subsequent PR will add the ability to read JSON strings directly, where this can be overcome as Perspective 2.x did - add a handler for these types to the default json module dumps() function.
• pandas.DataFrame is now handled by pyarrow, which needs to be installed for DataFrame type to work. Perspective implements no special inference/behavior for these, so it now inherits pyarrow's semantics regarding column types, precision, etc.

Rust Library

As a bonus which came together quite naturally, this PR also introduces a native Rust client and server for Perspective, which allows hosting the Perspective engine in e.g. axum, as well as the entirety of the Perspective API as previously implement for JavaScript and Python. The following new crates are introduced:

• perspective (native) has been repurposed as the root native-Rust crate, re-exporting the Rust Client and Server APIs as well as conveniences for linking the two with other libraries like tokio.
• perspective-python (native) contains the Python (pyO3) bindings, replacing the old C++ based perspective-python.
• perspective-server (native) wraps the C++ engine for both perspective and perspective-python.

An axum server example has also been added to the examples/ directory.