chore: Add permissions to auth data (#9695)

This API change sets the foundation for an upcoming frontend update, transitioning from a role-based model to a permission-based model. This new approach will determine eligibility for various actions and UI elements based on specific permissions rather than roles, enhancing flexibility and security in user access management.

spec/models/account_user_spec.rb

@@ -17,6 +17,17 @@ RSpec.describe AccountUser do
     end
   end
 
+  describe 'permissions' do
+    it 'returns the right permissions' do
+      expect(account_user.permissions).to eq(['agent'])
+    end
+
+    it 'returns the right permissions for administrator' do
+      account_user.administrator!
+      expect(account_user.permissions).to eq(['administrator'])
+    end
+  end
+
   describe 'destroy call agent::destroy service' do
     it 'gets created with the right default settings' do
       create(:conversation, account: account_user.account, assignee: account_user.user, inbox: inbox)