submissionDirectory path fix

src/main/java/de/hftstuttgart/dtabackend/utils/ExecuteTestUtil.java

@@ -50,7 +50,7 @@ public class ExecuteTestUtil {
 
     public ResultSummary runTests(String assignmentId, Path workDirectory) throws IOException, InterruptedException {
         // Define paths for the submission-specific directories
-        String submissionDirectory = this.basePathStudentsSubmissionCode + workDirectory.getFileName(); // /dta-test-assignments/dta-submissionID
+        String submissionDirectory = Paths.get(basePathStudentsSubmissionCode, workDirectory.getFileName().toString()).toString();
         Path testPath = Paths.get(submissionDirectory, "test");
         Path srcPath = Paths.get(submissionDirectory, "src");
         Path resultPath = Paths.get(submissionDirectory, "result");