input: Write a function to assign customers within a maximum capacity.
  assert assign_customers([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 8) == [1, 2, 3, 4]
  assert assign_customers([5, 1, 2, 3, 4], 10) == [5, 1, 2, 3]
  assert assign_customers([7, 2, 5, 4], 12) == [7, 2]
output: def assign_customers(customers, max_capacity):
      assigned_customers = []
      current_capacity = 0
      
      for customer in customers:
          if current_capacity + customer <= max_capacity:
              assigned_customers.append(customer)
              current_capacity += customer
          else:
              break
              
      return assigned_customers