class TimeTable
  include Mongoid::Document

  belongs_to :account, class_name: 'Account', inverse_of: :time_tables
  belongs_to :company_account, class_name: 'Account', inverse_of: :company_time_table, optional: true
end

class Account
  include Mongoid::Document

  has_one :company_time_table, class_name: 'TimeTable', inverse_of: :company_account, dependent: :destroy, validate: false
  has_many :time_tables, class_name: 'TimeTable', inverse_of: :account, dependent: :destroy, validate: false
end

account = Account.create!
ex_time_table = TimeTable.create(account:, company_account: account)
new_time_table = TimeTable.create(account:)

account.company_time_table = new_time_table # this codes produce the deletion of the ex_time_table document