Add comments controller and routes

app/models/post.rb

@@ -2,6 +2,7 @@ class Post < ApplicationRecord
   belongs_to :board
   belongs_to :user
   belongs_to :post_status, optional: true
+  has_many :comments
 
   validates :title, presence: true, length: { in: 4..64 }
 

app/models/user.rb

@@ -3,6 +3,8 @@ class User < ApplicationRecord
          :recoverable, :rememberable, :validatable,
          :confirmable
 
+  has_many :comments
+
   enum role: [:user, :moderator, :admin]
   after_initialize :set_default_role, if: :new_record?