Accept extra parameters at the HTTP handlers

The HTTP handlers now accept multiple parameters without invalidating
the signature token.

Issue: CW-1315

internal/service/worker.go

@@ -94,8 +94,13 @@ func (w *Worker) Process(
 		return fmt.Errorf("fail to fetch the file: %w", err)
 	}
 
+	if len(payload) == 0 {
+		return fmt.Errorf("empty payload")
+	}
+
 	storage := bytes.NewBuffer([]byte{})
-	err = lazypdf.SaveToPNG(ctx, uint16(page), uint16(width), scale, bytes.NewBuffer(payload), storage)
+	dpi := 96
+	err = lazypdf.SaveToPNG(ctx, uint16(page), uint16(width), scale, dpi, bytes.NewBuffer(payload), storage)
 	if err != nil {
 		return fmt.Errorf("fail to extract the PNG from the PDF: %w", err)
 	}

internal/service/worker_test.go

@@ -141,7 +141,7 @@ func TestWorkerProcess(t *testing.T) {
 				client.On("GetObjectWithContext", mock.Anything, &input).Return(&output, nil)
 				return &client
 			},
-			expectedError: "fail to extract the PNG from the PDF: failure at the C/MuPDF layer: cannot tell in file",
+			expectedError: "empty payload",
 		},
 		{
 			message: "process and return a page",

internal/transport/handler.go

@@ -86,7 +86,7 @@ func (h handler) document(w http.ResponseWriter, r *http.Request) {
 
 	path := strings.TrimPrefix(r.URL.Path, "/documents/")
 	buf := bytes.NewBuffer([]byte{})
-	err = h.documentService.Process(r.Context(), r.URL.String(), path, page, width, float32(scale), buf)
+	err = h.documentService.Process(r.Context(), h.urlToVerify(r), path, page, width, float32(scale), buf)
 	if ctxErr := r.Context().Err(); ctxErr != nil {
 		logger.Err(ctxErr).Str("requestID", reqID).Msg("Context error")
 		if ctxErr == context.Canceled {
@@ -124,7 +124,7 @@ func (h handler) metadata(w http.ResponseWriter, r *http.Request) {
 	}
 
 	path := strings.TrimPrefix(r.URL.Path, "/documents/")
-	fileName, pageCount, err := h.documentService.Metadata(r.Context(), r.URL.String(), path)
+	fileName, pageCount, err := h.documentService.Metadata(r.Context(), h.urlToVerify(r), path)
 	if ctxErr := r.Context().Err(); ctxErr != nil {
 		logger.Err(ctxErr).Str("requestID", reqID).Msg("Context error")
 		if ctxErr == context.Canceled {
@@ -150,3 +150,16 @@ func (h handler) metadata(w http.ResponseWriter, r *http.Request) {
 	}
 	h.writer.response(r.Context(), w, result, http.StatusOK)
 }
+
+// Remove all the parameters, but the token and page, from the path. Other parameters can then be passed to the service
+// without making the url signature invalid.
+func (h handler) urlToVerify(r *http.Request) string {
+	q := r.URL.Query()
+	for key := range q {
+		if key == "page" || key == "token" {
+			continue
+		}
+		q.Del(key)
+	}
+	return r.URL.String()
+}