feat: Ability to snooze conversations (#2682)

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

db/migrate/20210721182458_add_snoozed_until_to_conversations.rb

@@ -0,0 +1,5 @@
+class AddSnoozedUntilToConversations < ActiveRecord::Migration[6.0]
+  def change
+    add_column :conversations, :snoozed_until, :datetime
+  end
+end