Allows to open cvs files with umlauts

fixes #18

src/core/csvreader.cpp

@@ -11,8 +11,16 @@ std::size_t CsvReader::readSellersFromFile(const fs::path& filePath, Marketplace
     csv::CSVFormat format;
     format.delimiter(';');
 
+#if defined(_WIN64) || defined(_WIN32)
+    // Windows: Somhow this is necessary in order to open file names with umlauts
+    auto wide = filePath.wstring();
+    std::string fileName(wide.begin(), wide.end());
+
+    csv::CSVReader csvReader(fileName, format);
+#else
     csv::CSVReader csvReader(filePath.string(), format);
-    
+#endif
+
     for (auto& seller : market->getSellers()) {
         seller->setState(Seller::State::DELETE);
     }