Add on_write_progress

design.md

@@ -105,7 +105,6 @@ See `config.md` for complete configuration documentation.
 - **Safe shutdown mechanism** with async-signal-safe shutdown() method
 - **Connection ownership management** with automatic cleanup on server destruction
 - **Pluggable protocol handlers** via ConnectionHandler interface
-- TODO design a way to stream server sent events
 
 Key features:
 - Multi-threaded architecture: separate accept and network thread pools
@@ -135,7 +134,7 @@ Key features:
 - **Connection lifecycle hooks** for initialization and cleanup
 
 Key features:
-- process_data() with unique_ptr<Connection>& for ownership transfer
+- on_data_arrived()/on_write_progress() with unique_ptr<Connection>& for ownership transfer
 - on_connection_established/closed() hooks for protocol state management
 - Zero-copy data processing with arena allocator integration
 - Thread-safe ownership transfer via Server::releaseBackToServer()
@@ -282,7 +281,7 @@ The modular design allows each component to be optimized independently while mai
 
 ### Adding New Protocol Handlers
 - Inherit from `ConnectionHandler` in `src/connection_handler.hpp`
-- Implement `process_data()` with proper ownership semantics
+- Implement `on_data_arrived()` with proper ownership semantics
 - Use connection's arena allocator for temporary allocations: `conn->getArena()`
 - Handle partial messages and streaming protocols appropriately
 - Use `Server::releaseBackToServer()` if taking ownership for async processing
@@ -338,7 +337,7 @@ auto server = Server::create(config, handler);
 ```cpp
 class HttpHandler : public ConnectionHandler {
 public:
-  void process_data(std::string_view data, std::unique_ptr<Connection>& conn_ptr) override {
+  void on_data_arrived(std::string_view data, std::unique_ptr<Connection>& conn_ptr) override {
     // Parse HTTP request using connection's arena
     ArenaAllocator& arena = conn_ptr->getArena();
 
@@ -354,7 +353,7 @@ public:
 ```cpp
 class AsyncHandler : public ConnectionHandler {
 public:
-  void process_data(std::string_view data, std::unique_ptr<Connection>& conn_ptr) override {
+  void on_data_arrived(std::string_view data, std::unique_ptr<Connection>& conn_ptr) override {
     // Take ownership for async processing
     auto connection = std::move(conn_ptr); // conn_ptr is now null
 
@@ -369,6 +368,8 @@ public:
 };
 ```
 
+TODO add example of streaming data
+
 ### Arena-Based String Handling
 ```cpp
 // Preferred: Zero-copy string view with arena allocation