Add ical subscription

[david-venhoff]

Short description

This pr implements support for automatically creating events from an icalendar. This only implements step 1 of issue #100, as it is not currently possible to automatically use machine translation with this feature and we need another pr for that. However, it is possible to manually start machine translation for imported events.

For now, this feature is only visible to service team members and cms team members.

To test this pr, you could use this ical url, which includes events for july from Saarburg: https://www.saarburg.de/?post_type=tribe_events&tribe-bar-date=2024-07-08&ical=1&eventDisplay=list

Proposed changes

• Add a new model for external calendars, which contain an url to the ical file
• Add fields to the event model to specify whether this event was automatically imported, and link it to the icalendar
• Implement functionality for converting icalendar events into cms events and event translations
• Add UI for managing external calendars

Side effects

• We need a new cronjob that runs the import events command every once in a while

Resolved issues

Fixes: #100

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Pull Request Review Guidelines

[codeclimate]

Code Climate has analyzed commit aa41af7 and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 77.8% (50% is the threshold).

This pull request will bring the total coverage in the repository to 82.9% (0.0% change).

View more on Code Climate.

[JoeyStk]

#2850 is merged now :)

[david-venhoff]

Both blockers are now resolved :)

[JoeyStk]

Just two side notes: 1. This PR doesn't contain a release note, as we want to release this to the service team first without letting municipalities know about it (yet), 2. We want to do (1) so we test this very thoroughly and make sure everything works very smoothly before we let municipalities know about it. This makes is hopefully less daunting to review this PR :)

[MizukiTemma]

Thank you so much 💪 It looks a good start 😻

I have some suggestions but feel free to discard (or postpone if it is subject to planned extensions of the next step(s)).

1. Fixing width of the columns in the external calendar list (see screen shots below)
   We are getting this kind of fix requests time to time. Maybe better to implement it already now?

2. Checking the format of input in the field "URL"
   We have format check for the URL field of the model Organization. It probably makes sense here too?

3. Warning when the URL or tag of a calendar is about to be changed
   Events that are imported from the calendar and already saved will be deleted after changing those fields, if they do not match the URL and tag anymore. In my opinion warning before saving makes the system less confusing and safe.

[deen13]

First off, great job on this pull request! Your effort in tackling these issues is much appreciated. 🥳

General thoughts on the feature

• Prefetch Existing Tags: If possible, it might be useful to fetch all tags once the domain is entered. This way, tags could be presented as a combobox instead of a text field, which could help prevent errors.
• Import Error: There is an error occurring when importing events from Saarburg. The specific error is: Aug 01 08:46:13 ERROR integreat_cms.core.storages - An error occurred while importing events from this external calendar and Could not import 'Ausstellung Günter Schuster: Material und Sprache': The maximum duration for events is 28 days. Consider using recurring events if the event is not continuous.
• Django Cron: Pull Request Store delivered push notification count per region and language #2920 introduces django_cron, which could be beneficial for our use case.
• Event Review: It would be helpful to have an overview of all imported and erroneous events after import and before storing them. This would facilitate a thorough review process.
• Error Handling: The status column provides a detailed explanation of errors, but it's unclear how to handle them. Consider adding a popup for errors to provide more space if there are multiple issues.
• Error Management: Adding a button to clear reviewed errors would be useful so that subsequent users do not have to deal with errors that have already been addressed. This would also aid in identifying new errors during cron job polling.
• Security Considerations: Should we implement some form of verification for this feature to prevent domain takeover and malicious event injection? More on domain takeover vulnerabilities

[david-venhoff]

Thanks for your review!

Prefetch Existing Tags

This seems like a nice QoL improvement. However, that would not be a part of this pr, since we currently just intend to provide an mvp for the service team to test this feature. If everything works out, we will build on this mvp later.

Import error

I don't think there is much we can do about that. It has been a design decision to not allow events longer than 28 days in our system and the external calendar contains an event that is longer than that.

Django Cron

I didn't have a look at the pr yet, but that could be a nice alternative :)

Event Review

This could be a separate issue that we implement later

Error Handling

Same here

Error Management

Same here

Security Considerations

What is the threat you are thinking of? Are you worried that municipalities redirect to another provider for providing their icalendars? Because then I think it would be up to the municipalities to make sure that there are no security issues.
Or that municipalities enter the url of a third-party website, which might be malicious? That does not seem like a domain takeover vulnerability to me and also seems like it would be the responsibility of the municipalities to me.

[JoeyStk]

Warning when the URL or tag of a calendar is about to be changed
Events that are imported from the calendar and already saved will be deleted after changing those fields, if they do not match the URL and tag anymore. In my opinion warning before saving makes the system less confusing and safe.

I think this also would probably be something for a new issue :)

[MizukiTemma]

Warning when the URL or tag of a calendar is about to be changed
Events that are imported from the calendar and already saved will be deleted after changing those fields, if they do not match the URL and tag anymore. In my opinion warning before saving makes the system less confusing and safe.

I think this also would probably be something for a new issue :)

Ok 😉 Will you open an issue for that?

[JoeyStk]

Ok 😉 Will you open an issue for that?

Sure! It's the first comment in here :)

[MizukiTemma]

Thank you so much, looks good to me 😸 Let's merge and try 🚀

💡 Don't forget to squash, please.

[PeterNerlich]

This is mostly nitpicks and nothing serious blocking this PR, especially since this is more like just a prove of concept to see if we move forward with this idea.

Another such nitpick is that the tests cover the command itself and the permissions for the views, but not that the view actually triggers the same functionality.