feat: add job to remove stale contacts and contact_inboxes (#11186)

- Add a job to remove stale contacts and contact_inboxes across all accounts

Stale anonymous contact is defined as 
- have no identification (email, phone_number, and identifier are NULL)
- have no conversations
- are older than 30 days

---------

Co-authored-by: Pranav <pranav@chatwoot.com>
Co-authored-by: Shivam Mishra <scm.mymail@gmail.com>

app/models/contact.rb

@@ -128,6 +128,18 @@ class Contact < ApplicationRecord
     )
   }
 
+  # Find contacts that:
+  # 1. Have no identification (email, phone_number, and identifier are NULL or empty string)
+  # 2. Have no conversations
+  # 3. Are older than the specified time period
+  scope :stale_without_conversations, lambda { |time_period|
+    where('contacts.email IS NULL OR contacts.email = ?', '')
+      .where('contacts.phone_number IS NULL OR contacts.phone_number = ?', '')
+      .where('contacts.identifier IS NULL OR contacts.identifier = ?', '')
+      .where('contacts.created_at < ?', time_period)
+      .where.missing(:conversations)
+  }
+
   def get_source_id(inbox_id)
     contact_inboxes.find_by!(inbox_id: inbox_id).source_id
   end