feat: Add reverse proxy functionality with enhanced routing capabilities

- Introduced IgnoreRequestPath option in proxy configuration to allow exact match routing.
- Implemented proxy_pass directive in routing extension to handle backend requests.
- Enhanced error handling for backend unavailability and timeouts.
- Added integration tests for reverse proxy, including basic requests, exact match routes, regex routes, header forwarding, and query string preservation.
- Created helper functions for setting up test servers and backends, along with assertion utilities for response validation.
- Updated server initialization to support extension management and middleware chaining.
- Improved logging for debugging purposes during request handling.

go/internal/proxy/proxy.go

@@ -29,6 +29,10 @@ type Config struct {
 
 	// PreserveHost keeps the original Host header
 	PreserveHost bool
+
+	// IgnoreRequestPath ignores the request path and uses only the target path
+	// This is useful for exact match routes where target URL should be used as-is
+	IgnoreRequestPath bool
 }
 
 type ReverseProxy struct {
@@ -116,6 +120,13 @@ func (rp *ReverseProxy) ProxyRequest(w http.ResponseWriter, r *http.Request, par
 func (rp *ReverseProxy) buildTargetURL(r *http.Request) *url.URL {
 	targetURL := *rp.targetURL
 
+	// If ignoring request path, use target URL path as-is
+	if rp.config.IgnoreRequestPath {
+		// Preserve query string only
+		targetURL.RawQuery = r.URL.RawQuery
+		return &targetURL
+	}
+
 	// Strip prefix if configured
 	path := r.URL.Path
 	if rp.config.StripPrefix != "" {
@@ -125,10 +136,12 @@ func (rp *ReverseProxy) buildTargetURL(r *http.Request) *url.URL {
 		}
 	}
 
-	// If target has a path, append request path to it
+	// If target URL has a non-empty path, combine it with the request path
 	if rp.targetURL.Path != "" && rp.targetURL.Path != "/" {
-		targetURL.Path = singleJoiningSlash(rp.targetURL.Path, path)
+		// Combine target path with request path
+		targetURL.Path = strings.TrimSuffix(rp.targetURL.Path, "/") + path
 	} else {
+		// No path in target, use request path as-is
 		targetURL.Path = path
 	}