fix(wopi): cannot set preferred language for LibreOffice online

pkg/wopi/wopi.go

@@ -59,6 +59,7 @@ const (
 
 	wopiSrcPlaceholder    = "WOPI_SOURCE"
 	wopiSrcParamDefault   = "WOPISrc"
+	languageParamDefault  = "lang"
 	sessionExpiresPadding = 10
 	wopiHeaderPrefix      = "X-WOPI-"
 )
@@ -214,6 +215,9 @@ func generateActionUrl(src string, fileSrc string) (*url.URL, error) {
 		queryReplaced.Set(wopiSrcParamDefault, fileSrc)
 	}
 
+	// LibreOffice require this flag to show correct language
+	queryReplaced.Set(languageParamDefault, "lng")
+
 	actionUrl.RawQuery = queryReplaced.Encode()
 	return actionUrl, nil
 }