fix(zarinhub): limit upstream response size

backend/internal/zarinhub/client_test.go

@@ -381,3 +381,36 @@ func TestClientReturnsTimeout(t *testing.T) {
 		)
 	}
 }
+
+func TestClientRejectsOversizedResponse(t *testing.T) {
+	server := httptest.NewServer(
+		http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.WriteHeader(http.StatusOK)
+
+			body := make([]byte, maxResponseBodySize+1)
+			for index := range body {
+				body[index] = 'x'
+			}
+
+			if _, err := w.Write(body); err != nil {
+				t.Errorf("write response: %v", err)
+			}
+		}),
+	)
+	defer server.Close()
+
+	client := NewClient(
+		&http.Client{Timeout: time.Second},
+		server.URL,
+		"test-token",
+	)
+
+	_, err := client.Convert(
+		context.Background(),
+		"6037997512345678",
+	)
+
+	if !errors.Is(err, ErrInvalidResponse) {
+		t.Fatalf("error = %v, want ErrInvalidResponse", err)
+	}
+}