chore: Improve n+1 queries (#4202)

Fixes the n+1 queries that get triggered while accessing agents endpoint

app/controllers/api/v1/accounts/agents_controller.rb

@@ -68,7 +68,7 @@ class Api::V1::Accounts::AgentsController < Api::V1::Accounts::BaseController
   end
 
   def agents
-    @agents ||= Current.account.users.order_by_full_name.includes({ avatar_attachment: [:blob] })
+    @agents ||= Current.account.users.order_by_full_name.includes(:account_users, { avatar_attachment: [:blob] })
   end
 
   def validate_limit

app/models/user.rb

@@ -108,7 +108,9 @@ class User < ApplicationRecord
   end
 
   def current_account_user
-    account_users.find_by(account_id: Current.account.id) if Current.account
+    # We want to avoid subsequent queries in case where the association is preloaded.
+    # using where here will trigger n+1 queries.
+    account_users.find { |ac_usr| ac_usr.account_id == Current.account.id } if Current.account
   end
 
   def available_name

app/views/api/v1/models/_agent.json.jbuilder

@@ -1,6 +1,6 @@
 json.id resource.id
 # could be nil for a deleted agent hence the safe operator before account id
-json.account_id resource.account&.id
+json.account_id Current.account&.id
 json.availability_status resource.availability_status
 json.auto_offline resource.auto_offline
 json.confirmed resource.confirmed?