fix: Get online status from db when not present in cache [CW-3233] (#9477)

Previously, we returned the static value 'online' when the status was
not present in the Redis cache. This PR changes it to fall back to the
DB value and updates the cache in such cases.

fixes:
https://linear.app/chatwoot/issue/CW-3233/write-a-back-up-for-online-status-in-case-if-redis-keys-are-not

lib/online_status_tracker.rb

@@ -57,7 +57,13 @@ class OnlineStatusTracker
     return {} if user_ids.blank?
 
     user_availabilities = ::Redis::Alfred.hmget(status_key(account_id), user_ids)
-    user_ids.map.with_index { |id, index| [id, (user_availabilities[index] || 'online')] }.to_h
+    user_ids.map.with_index { |id, index| [id, (user_availabilities[index] || get_availability_from_db(account_id, id))] }.to_h
+  end
+
+  def self.get_availability_from_db(account_id, user_id)
+    availability = Account.find(account_id).account_users.find_by(user_id: user_id).availability
+    set_status(account_id, user_id, availability)
+    availability
   end
 
   def self.get_available_user_ids(account_id)