Step to reproduce: 1. `a n/Test2 e/test2@gmail.com m/CS2100XX`  Result: - Contact is added nonetheless because add command allows for module code with more than one-letter suffix as stated below  <!--session: 1635494520381-f82c7867-fe60-474c-893b-d45e97e03efe--> <!--Version: Web v3.4.1-->