Rework 0.3 handlers and worlds

- Add an `outgoing-handler` interface with the same type as `handler`
- Replace the `imports` world's `handler` import with `outgoing-handler`
- Replace the `proxy` world with `service`
- Add a `middleware` world

Author: lann

wit-0.3.0-draft/handler.wit

@@ -1,17 +1,27 @@
-/// This interface defines a handler of HTTP Requests.  It may be imported by
-/// components which wish to send HTTP Requests and also exported by components
-/// which can respond to HTTP Requests.  In addition, it may be used to pass
-/// a request from one component to another without any use of a network.
+/// This interface defines a handler of HTTP Requests. It may be exported by
+/// components which can respond to HTTP Requests. In addition, it may be
+/// imported by components to wrap another `handler` as with "middleware".
 interface handler {
   use types.{request, response, error-code};
 
-  /// When exported, this function may be called with either an incoming
-  /// request read from the network or a request synthesized or forwarded by
-  /// another component.
-  ///
-  /// When imported, this function may be used to either send an outgoing
-  /// request over the network or pass it to another component.
+  /// This function may be called with either an incoming request read from the
+  /// network or a request synthesized or forwarded by another component.
   handle: async func(
     request: request,
   ) -> result<response, error-code>;
 }
+
+/// This interface defines a handler of "outgoing" HTTP Requests. It may be
+/// imported by components that wish to send HTTP Requests or it may be
+/// composed with a `handler` to process requests without any use of a network.
+/// In addition, it may be exported by components to wrap another
+/// `outgoing-handler` as with "client interceptors".
+interface outgoing-handler {
+  use types.{request, response, error-code};
+
+  /// This function may be used to either send an outgoing request over the
+  /// network or to forward it to another component.
+  handle: async func(
+    request: request,
+  ) -> result<response, error-code>;
+}

wit-0.3.0-draft/proxy.wit renamed to wit-0.3.0-draft/service.wit

@@ -1,13 +1,13 @@
 package wasi:http@0.3.0-rc-2025-09-16;
 
-/// The `wasi:http/imports` world imports all the APIs for HTTP proxies.
+/// The `wasi:http/imports` world imports all the APIs for HTTP services.
 /// It is intended to be `include`d in other worlds.
 world imports {
-  /// HTTP proxies have access to time and randomness.
+  /// HTTP services have access to time and randomness.
   include wasi:clocks/imports@0.3.0-rc-2025-09-16;
   import wasi:random/random@0.3.0-rc-2025-09-16;
 
-  /// Proxies have standard output and error streams which are expected to
+  /// Services have standard output and error streams which are expected to
   /// terminate in a developer-facing console provided by the host.
   import wasi:cli/stdout@0.3.0-rc-2025-09-16;
   import wasi:cli/stderr@0.3.0-rc-2025-09-16;
@@ -18,19 +18,15 @@ world imports {
   /// when this import is properly removed.
   import wasi:cli/stdin@0.3.0-rc-2025-09-16;
 
-  /// This is the default handler to use when user code simply wants to make an
-  /// HTTP request (e.g., via `fetch()`).
-  ///
-  /// This may also be used to pass synthesized or forwarded requests to another
-  /// component.
-  import handler;
+  /// This is the default `outgoing-handler` to use when user code simply wants
+  /// to make an HTTP request (e.g., via `fetch()`).
+  import outgoing-handler;
 }
 
-/// The `wasi:http/proxy` world captures a widely-implementable intersection of
-/// hosts that includes HTTP forward and reverse proxies. Components targeting
-/// this world may concurrently stream in and out any number of incoming and
-/// outgoing HTTP requests.
-world proxy {
+/// The `wasi:http/service` world captures a broad category of HTTP services
+/// including web applications, API servers, and proxies. It may be `include`d
+/// in more specific worlds such as `wasi:http/gateway`.
+world service {
   include imports;
 
   /// The host delivers incoming HTTP requests to a component by calling the
@@ -42,3 +38,13 @@ world proxy {
   /// another component.
   export handler;
 }
+
+/// The `wasi:http/middleware` world captures HTTP services that forward HTTP
+/// Requests to another handler. Components may implement this world to allow
+/// them to participate in handler "chains" where a Request flows through
+/// handlers on its way to some "terminal" service and corresponding Responses
+/// flow in the opposite direction.
+world middleware {
+  include service;
+  import handler;
+}