Add compression support

[davebelais]

This pull request adds support for additional content encodings (zstd and brotli) in HTTP request and response handling, improves the robustness of content encoding/decoding logic, and updates dependencies accordingly. The changes affect both the core functionality in src/oapi/client.py and the project configuration to ensure the new features work out-of-the-box.

Content Encoding/Decoding Enhancements:

• Added _encode_content and _decode_content helper functions to support gzip, zstd, and brotli (including brotlicffi fallback) for encoding and decoding HTTP request and response bodies, including proper handling of multiple/stacked encodings.
• Updated request and response handling logic throughout src/oapi/client.py to use the new helpers, ensuring that content is automatically encoded or decoded based on the Content-Encoding header. [1] [2] [3] [4] [5] [6]
• Improved detection of content type and encoding in request/response processing, making header lookups case-insensitive and more robust.

Dependency and Packaging Updates:

• Added zstandard, brotli, and brotlicffi as optional dependencies in pyproject.toml, and included them in the all feature for easy installation.
• Updated the minimum required version of sob to 2.2 and bumped the package version to 2.8.0. [1] [2]
• Updated the upgrade target in the Makefile to include the all feature, ensuring all optional dependencies are handled during upgrades.
• Added a features = ["all"] entry to the default environment in pyproject.toml to ensure all features are available in development and CI.

Other Improvements:

• Simplified logic for adding --compressed to curl options in the request callback, now enabling it for any Content-Encoding header (not just gzip).