title: Self association with accepted nested attributes
body: <pre><code>class Employee &lt; ApplicationRecord
    has_many :subordinates, class_name: "Employee", foreign_key: "manager_id"
    belongs_to :manager, class_name: "Employee", optional: true
    accepts_nested_attributes_for :subordinates
  end
  </code></pre>
  
  <p>How to create employee_params in controller for deep nested association like above.</p>
  
  <pre><code>def employee_params
    params.require(:employee).permit(:name, :roll_no, subordinates_attributes: [:name, roll_no, :subordate_attributes:[]......])
  end
  </code></pre>