table naming

create_sellers.rb

class CreateSellers < ActiveRecord::Migration
  def change
    create_table :sellers do |t|
      t.integer :manager_id
      t.integer :address_id

      t.timestamps
    end
  end
end

seller.rb

# app/models/spree/seller.rb
module Spree
  class Seller < ActiveRecord::Base
    belongs_to :user, :foreign_key => 'manager_id'
    belongs_to :address

    has_many :orders

  end
end