feat: Line Channel (#2904)

- Ability to configure line bots as a channel in chatwoot
- Receive a message sent to the line bot in chatwoot
- Ability to reply to line users from chatwoot

fixes: #2738

app/models/concerns/channelable.rb

@@ -0,0 +1,12 @@
+module Channelable
+  extend ActiveSupport::Concern
+  included do
+    validates :account_id, presence: true
+    belongs_to :account
+    has_one :inbox, as: :channel, dependent: :destroy
+  end
+
+  def has_24_hour_messaging_window?
+    false
+  end
+end