Proxy-SDK

A rewrite of the proxy-wasm rust crate. Has improved ergonomics, more type safety, and documentation.

Proxy->WASM Calls Not Implemented

• validate_configuration: Seems unused
• on_request_metadata: Unused
• on_response_metadata: Unused
• on_grpc_create_initial_metadata: Never called/incompletely defined in proxy-wasm-cpp-host
• on_foreign_function: Never called from Envoy outside of tests

Feature Flags

• stream-metadata, if enabled, enables GRPC metadata callbacks. Known to cause crashes in some versions of Envoy.