fix:#46 updated fetcher and empty course issue

services/data-manager/service/fetch/v1/fetchSeminarGroupService.go

@@ -89,8 +89,9 @@ func removeDuplicates(groups db.SeminarGroups) db.SeminarGroups {
 	uniqueGroups := make(db.SeminarGroups, 0, len(groups))
 	seen := make(map[string]struct{}) // Use an empty struct to minimize memory usage
 
+	// unique Identifier is the course and semester
 	for _, group := range groups {
-		key := group.Course + group.Semester
+		key := group.UniqueKey()
 		if _, exists := seen[key]; !exists {
 			seen[key] = struct{}{}
 			uniqueGroups = append(uniqueGroups, group)