chore: Introduce enterprise edition license (#3209)

- Initialize an "enterprise" folder that is copyrighted.
- You can remove this folder and the system will continue functioning normally, in case you want a purely MIT licensed product.
- Enable limit on the number of user accounts in enterprise code.
- Use enterprise edition injector methods (inspired from Gitlab).
- SaaS software would run enterprise edition software always.

Co-authored-by: Pranav Raj S <pranav@chatwoot.com>

lib/chatwoot_app.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+require 'pathname'
+
+module ChatwootApp
+  def self.root
+    Pathname.new(File.expand_path('..', __dir__))
+  end
+
+  def self.max_limit
+    100_000
+  end
+
+  def self.enterprise?
+    return if ENV.fetch('DISABLE_ENTERPRISE', false)
+
+    @enterprise ||= root.join('enterprise').exist?
+  end
+
+  def self.custom?
+    @custom ||= root.join('custom').exist?
+  end
+
+  def self.extensions
+    if custom?
+      %w[enterprise custom]
+    elsif enterprise?
+      %w[enterprise]
+    else
+      %w[]
+    end
+  end
+end

lib/custom_exceptions/account.rb

@@ -28,4 +28,10 @@ module CustomExceptions::Account
       I18n.t 'errors.signup.failed'
     end
   end
+
+  class PlanUpgradeRequired < CustomExceptions::Base
+    def message
+      I18n.t 'errors.plan_upgrade_required.failed'
+    end
+  end
 end