feat(chromium): add validation of 'emulatedMediaType' form field at the handler level

pkg/modules/chromium/routes.go

@@ -62,7 +62,21 @@ func FormDataChromiumPDFOptions(ctx *api.Context) (*api.FormData, Options) {
 
 			return nil
 		}).
-		String("emulatedMediaType", &emulatedMediaType, defaultOptions.EmulatedMediaType).
+		Custom("emulatedMediaType", func(value string) error {
+			if value == "" {
+				emulatedMediaType = defaultOptions.EmulatedMediaType
+
+				return nil
+			}
+
+			if value != "screen" && value != "print" {
+				return fmt.Errorf("wrong value, expected either 'screen', 'print' or empty")
+			}
+
+			emulatedMediaType = value
+
+			return nil
+		}).
 		Bool("landscape", &landscape, defaultOptions.Landscape).
 		Bool("printBackground", &printBackground, defaultOptions.PrintBackground).
 		Float64("scale", &scale, defaultOptions.Scale).
@@ -493,16 +507,6 @@ func convertURL(ctx *api.Context, chromium API, engine gotenberg.PDFEngine, URL,
 			)
 		}
 
-		if errors.Is(err, ErrInvalidEmulatedMediaType) {
-			return api.WrapError(
-				fmt.Errorf("convert to PDF: %w", err),
-				api.NewSentinelHTTPError(
-					http.StatusBadRequest,
-					fmt.Sprintf("The media type '%s' (emulatedMediaType) is invalid: allowed values are 'screen' or 'print'", options.EmulatedMediaType),
-				),
-			)
-		}
-
 		if errors.Is(err, ErrInvalidEvaluationExpression) {
 			if options.WaitForExpression == "" {
 				// We do not expect the 'waitWindowStatus' form field to return