Add circle editor

app/models/circle.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+# == Schema Information
+#
+# Table name: circles
+#
+#  id         :bigint(8)        not null, primary key
+#  account_id :bigint(8)        not null
+#  title      :string           default(""), not null
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#
+
+class Circle < ApplicationRecord
+  include Paginable
+
+  PER_ACCOUNT_LIMIT = 100
+
+  belongs_to :account
+
+  has_many :circle_accounts, inverse_of: :circle, dependent: :destroy
+  has_many :accounts, through: :circle_accounts
+
+  validates :title, presence: true
+
+  validates_each :account_id, on: :create do |record, _attr, value|
+    record.errors.add(:base, I18n.t('lists.errors.limit')) if List.where(account_id: value).count >= PER_ACCOUNT_LIMIT
+  end
+end