[v4] support error handling flow like gRPC (#158)

* add status package with tests and integrate into response parsing
* improve unit-tests
* improve readme

status/status.go

@@ -0,0 +1,54 @@
+package status
+
+import (
+	"errors"
+	"fmt"
+	"net/http"
+)
+
+// Status represents the outcome of an HTTP request in a style similar to gRPC status.
+type Status struct {
+	code    int    // HTTP status code
+	message string // HTTP status text
+	details any    // parsed error object
+}
+
+func New(statusCode int) *Status {
+	return &Status{code: statusCode, message: http.StatusText(statusCode)}
+}
+
+func FromError(err error) (*Status, bool) {
+	if err == nil {
+		return nil, false
+	}
+	var e *Error
+	if errors.As(err, &e) {
+		return e.HTTPStatus(), true
+	}
+	return nil, false
+}
+
+func (s *Status) Code() int {
+	return s.code
+}
+
+func (s *Status) Message() string {
+	return s.message
+}
+
+func (s *Status) Details() any {
+	return s.details
+}
+
+func (s *Status) WithDetails(details any) *Status {
+	s.details = details
+	return s
+}
+
+func (s *Status) String() string {
+	return fmt.Sprintf("http error: code = %d desc = %s", s.Code(), s.Message())
+}
+
+func (s *Status) Err() error {
+	return &Error{s: s}
+}