Begin of the insertionIn the appsignal error, the `Calendar::ICalController#show` endpoint is called with a token which refers a `Token::ICal` record which references a user who does no longer exist (the anonymous user with user\_id being 2).

End of the insertion ### Steps to reproduce

* Begin of the insertionCreate a user

* Create a calendar in a project with that user

* Subscribe to the calendar (from "···" menu, select "Subscribe to calendar")

* If you don't want to use a real calendar app, use `curl` to check that the ical url works

* for instance `curl -s -I <url> | grep HTTP` to get only the response code

* should see `HTTP/1.1 200 OK`

* Delete the user

* Use the `curl` command againEnd of the insertion Begin of the deletion Unclear - AppSignal reportEnd of the deletion


### What is the buggy behavior?

* Begin of the insertionAn exception is triggered: &quot;NoMethodError (undefined method &#39;time\_zone&#39; for nil)&quot;

* `HTTP/1.1 500 Internal Server Error`

* It happens because the user has been (soft-)deleted, but the token still existsEnd of the insertion Begin of the deletion Unclear - AppSignal reportEnd of the deletion


### What is the expected behavior?

* Unclear - AppSignal report Begin of the insertion

* It should return a 404: as the user does not exist, the ical subscription is not found.

* Additionnally, when a user gets deleted, the associated tokens should be deleted.

* Add code to properly delete tokens when user is deleted

* Add migration to clean dangling tokens

* Add migration to add foreign key constraint from tokens to users

* Actually, the constraint already exists, but the user being soft-deleted, the constraint is respected but the user cannot be found.


<br>

* Bonus question: if user is locked / inactive, should this endpoint return 404 as well?End of the insertion


### **Logs**

[https://appsignal.com/openproject-gmbh/sites/673c529383eb67b55471dda2/exceptions/incidents/1326/samples/last](https://appsignal.com/openproject-gmbh/sites/673c529383eb67b55471dda2/exceptions/incidents/1326/samples/last)

```text
lib/open_project/locale_helper.rb:34 OpenProject::LocaleHelper.with_locale_for
app/models/user.rb:546 User.execute_as
modules/calendar/app/services/calendar/ical_response_service.rb:48 Calendar::ICalResponseService#perform
app/services/base_services/base_callable.rb:42 block in BaseServices::BaseCallable#call
app/services/base_services/base_callable.rb:70 BaseServices::BaseCallable#assign_state
app/services/base_services/base_callable.rb:41 BaseServices::BaseCallable#call
modules/calendar/app/controllers/calendar/ical_controller.rb:36 Calendar::ICalController#show
vendor/plugins/openproject-multitenancy/lib/multitenancy/elevators/mapped_domain_elevator.rb:106 block in Multitenancy::Elevators::MappedDomainElevator#call_tenant
vendor/plugins/openproject-multitenancy/lib/multitenancy/elevators/mapped_domain_elevator.rb:103 Multitenancy::Elevators::MappedDomainElevator#call_tenant
vendor/plugins/openproject-multitenancy/lib/multitenancy/elevators/mapped_domain_elevator.rb:69 Multitenancy::Elevators::MappedDomainElevator#try_tenant
vendor/plugins/openproject-multitenancy/lib/multitenancy/elevators/mapped_domain_elevator.rb:39 Multitenancy::Elevators::MappedDomainElevator#call
```