public async Task DeleteAsync(Guid settlementId, Guid userId, Guid expenseId)
{
var settlement = await _settlementRepository.GetSettlementOrFailAsync(settlementId);
var userExpense = settlement.GetUserExpense(userId, expenseId);
await _settlementRepository.DeleteExpenseAsync(settlementId, userExpense);
var user = await _userRepository.GetAsync(userId);
user.RemoveSettlement(settlementId);
}