✨ Refactor ResponseHelper and add ResponderHandler

- Modified ResponseHelper.Body signature to return an io.Reader and an error.
- Updated ResponseHandler.ServeHTTP to handle errors from ResponseHelper.Body.
- Implemented JSONResponse and JSONResponseWithStatus functions for easier JSON responses.
- Added comprehensive unit tests for JSON response handling, including error scenarios.
- Extended Helper.ResponderHandler with a new test case to ensure proper error handling and response generation.
- Resolved linting issues related to dynamic error definition and function length in tests.

handler.go

@@ -1,13 +1,44 @@
 package ezhandler
 
-import "net/http"
+import (
+	"io"
+	"net/http"
+)
 
+// Handler is similar to [http.Handler], but also may return an error.
 type Handler interface {
 	ServeHTTP(w http.ResponseWriter, r *http.Request) error
 }
 
+// HandlerFunc is similar to [http.HandlerFunc] but it can also return an error.
 type HandlerFunc func(w http.ResponseWriter, r *http.Request) error
 
+var _ Handler = HandlerFunc(nil)
+
 func (fn HandlerFunc) ServeHTTP(w http.ResponseWriter, r *http.Request) error {
 	return fn(w, r)
 }
+
+// ResponseHandler is similar to HandlerFunc but returns a [ResponseHelper], instead of passing an [http.ResponseWriter].
+type ResponseHandler func(r *http.Request) (resp ResponseHelper, err error)
+
+var _ Handler = ResponseHandler(nil)
+
+func (fn ResponseHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) error {
+	resp, err := fn(r)
+	if err != nil {
+		return err
+	}
+	w.WriteHeader(resp.Status())
+	for key, values := range resp.Headers() {
+		for _, val := range values {
+			w.Header().Add(key, val)
+		}
+	}
+	body, err := resp.Body()
+	if err != nil {
+		return err
+	}
+	_, err = io.Copy(w, body)
+	return err
+}