v0.2.0 - Hore Async LFG

Breaking Changes

Major Architecture Change: Thread Pool to Async

The library has been completely refactored from a thread pool-based
implementation to an async/tokio-based architecture. This is a major breaking
change.

API Changes:

• Server::new() replaced with Methods::new()

• server.register() replaced with methods.add()

• server.run() replaced with json_rpc::serve(transport, methods)

• Method handlers must now be async functions instead of sync closures

• Example:

  // Old API
  server.register("add", |params: (i32, i32)| {
      Ok(params.0 + params.1)
  })?;
  server.run()?;
  
  // New API
  methods.add("add", |params: (i32, i32)| async move {
      Ok(params.0 + params.1)
  });
  json_rpc::serve(transport, methods).await?;

Removed Features:

• Thread pool configuration (concurrency now handled by tokio's task scheduler)
• ShutdownSignal for graceful server shutdown
• CancellationToken for request cancellation
• with_thread_pool_size() method
• with_shutdown_signal() method
• with_transport() method (transport now passed to serve())
• Server type and all its methods

New Features:

• Full async/await support built on tokio
• HTTP transport using axum web framework
• Improved transport abstraction - each transport implements its own serving
  logic
• Better separation of concerns between protocol handling and transport

Module Changes:

• src/server.rs removed (functionality moved to lib.rs and transports)
• src/shutdown.rs removed
• src/cancellation.rs removed
• src/methods.rs added (method registry with builder pattern)
• src/transports/http.rs added (new HTTP transport)

Dependency Changes:

• Added: tokio (1.0) - async runtime
• Added: axum (0.7) - HTTP web server framework
• Removed: num_cpus - no longer needed
• Removed: assert_cmd - testing infrastructure changed

Migration Guide:

To migrate from the old thread pool-based API:

1. Add tokio to your Cargo.toml with features = ["full"]
2. Change all method handlers to async functions
3. Replace Server::new() with Methods::new()
4. Replace server.register() calls with methods.add()
5. Replace server.run() with json_rpc::serve(transport, methods).await
6. Remove any shutdown signal or cancellation token usage
7. Update to use one of the three transports: Stdio, Http, or InMemory