Change findByEppn return type to list

bwreg-service/src/main/java/edu/kit/scc/webreg/service/impl/UserUpdateServiceImpl.java

@@ -342,11 +342,14 @@ public class UserUpdateServiceImpl implements UserUpdateService, Serializable {
 	}
 
 	private UserEntity findUser(String eppn) {
-		UserEntity user = userDao.findByEppn(eppn);
+		List<UserEntity> userList = userDao.findByEppn(eppn);
+		if (userList.size() == 0)
+			return null;
+		else if (userList.size() > 1)
+			return null;
 
-		if (user != null) {
-			user = userDao.findByIdWithStore(user.getId());
-		}
+		UserEntity user = userList.get(0);
+		user = userDao.findByIdWithStore(user.getId());
 
 		return user;
 	}

bwreg-service/src/main/java/edu/kit/scc/webreg/service/twofa/TwoFaLoginServiceImpl.java

@@ -63,9 +63,12 @@ public class TwoFaLoginServiceImpl implements TwoFaLoginService {
 		
 		if (eppn != null) {
 			if (eppn.contains("@")) {
-				user = userDao.findByEppn(eppn);
-				if (user == null)
+				List<UserEntity> userList = userDao.findByEppn(eppn);
+				if (userList.size() == 0)
 					throw new NoUserFoundException("no such user");
+				else if (userList.size() > 1)
+					throw new NoUserFoundException("user eppn not unique");
+				user = userList.get(0);
 				
 				registry = findRegistry(user, service);
 				if (registry == null)