feat: Simple publishing beginning and end dates

[fsbraun]

Description

Based on the discussion #340 this PR uses the power of djangocms-versionings' abstraction and introduces an option to limit the visibility of a published content object in time.

UX

• New option to publish from the versioning menu (The "Publish" button does not change behavior.)

• The menu brings up a modal allowing to select time limits for the visibility of the to-be-published version:

• Technically, the time limits do not affect the published status but only the visibility. This means, dates on published versions cannot be changed any more. You'd need to create a new draft and publish that to make a change.

• Versioning menu shows pending or expired visibility dates. "pending" is a word for a published version that is not yet visible. "expired" is a word for a published version not visible any more:

• View published button for PageContents is only offered for pages which are currently visible (since otherwise they'll show a 404)

• Pending or expired aliases render empty.

Tests

This is a proof of concept for discussion. Tests will need to be added and also some informaion on the changelist for versions.

Tests fail since the version admin's publish_view now also accepts a GET request which renders the form for time limits. Tests have now been adjusted, yet

Issues

• Missing tests
• Menu caching

Related resources

• #340

Checklist

• [x] I have opened this pull request against master
• [ ] I have added or modified the tests when changing logic
• [x] I have followed the conventional commits guidelines to add meaningful information into the changelog
• [x] I have read the contribution guidelines and I have joined #workgroup-pr-review on Slack to find a “pr review buddy” who is going to review my pull request.

[marksweb]

Yes, that point about it providing an example of how to extend functionality is real key one thay we should be able to demonstrate at launch.

And I don't actually know how it's done yet. I'd have a stab at it if I did.

I've got more thoughts but little time. The spiral of complexity is a big one. And nobody has even brought up timezones yet. 😬

[jrief]

Thanks for adding this important missing piece to djangocms-versioning. I just tested this pull request, but there are some issues:

• If an anonymous (or non-editing) user access a page which has status="pending", in my opinion it should either send status 404, or better 410 - Gone. Instead the user receives a page without content.
• The list view for versions should also display status="pending" rather than "published", otherwise it becomes very confusing for the editor because he doesn't recognize that a designated "published" version in reality is still pending. This information is only available when visiting the page directly.

@Aiky30 I get your point about separating this feature into another package. However, how would you implement it? And since it seems that some work has already been done, is this available?

I probably will implement this PR into our installation anyway, because it's a feature our users expect since it was available in CMS3. And I can't wait until a new package emerges anytime.