I dont think association will be forced to validate automatically, I think it was incorrect logic, how can i remove it instantly ??

$ irb
```
require 'mongoid'
=> true

class Customer
include Mongoid::Document
belongs_to :agent
end

Customer.validators
=> [#<Mongoid::Validatable::PresenceValidator:0x007fc2b04fe438 @attributes=[:agent], @options={}>]

customer = Customer.new
customer._validators
=> {:agent=>[#<Mongoid::Validatable::PresenceValidator:0x007fc2b04fe438 @attributes=[:agent], @options={}>]}

customer.valid?
=> false

customer.errors.full_messages
=> ["Agent can't be blank"]

```