Added missing @Transactional

With the migration to Spring it is much stricter in requiring @Transactional for all methods that write to the database.

core/src/main/java/se/su/dsv/scipro/plagiarism/urkund/UrkundSubmissionRepositoryImpl.java

@@ -1,6 +1,7 @@
 package se.su.dsv.scipro.plagiarism.urkund;
 
 import com.querydsl.jpa.impl.JPAQuery;
+import jakarta.transaction.Transactional;
 import se.su.dsv.scipro.file.FileDescription;
 
 import jakarta.inject.Inject;
@@ -27,6 +28,7 @@ public class UrkundSubmissionRepositoryImpl implements UrkundSubmissionRepositor
     }
 
     @Override
+    @Transactional
     public UrkundSubmission save(final UrkundSubmission submission) {
         final EntityManager em = entityManagerProvider.get();
         if (em.contains(submission)) {
@@ -49,6 +51,7 @@ public class UrkundSubmissionRepositoryImpl implements UrkundSubmissionRepositor
     }
 
     @Override
+    @Transactional
     public void delete(final UrkundSubmission urkundSubmission) {
         entityManagerProvider.get().remove(urkundSubmission);
     }