Expose user lists via CalDAV.

Describe your suggested feature

This application allows the user to create "to watch" and "watched" lists. However, these cannot be accessed by the user in a uniform manner with their other tasks lists. This is problematic for me, because it prevents me knowing cohesively what I still have yet to watch alongside the things that I track elsewhere (for instance, if unavailable via this application).

Other details

Would depend upon https://github.com/recloudstream/cloudstream/issues/549#issue-1847125505, I expect.

https://github.com/bookwyrm-social/bookwyrm/issues/2952#issue-1847099016

Additional context

Read-only exposure would easily be enough for me, at least for now, because it would still allow me to easily see offline what's in each list, although it wouldn't allow me to cache offline changes to later be applied when online, like modification support would.

Relevant:

0. https://gitlab.com/gitlab-org/gitlab/-/issues/14390
1. https://github.com/kaleidos-ventures/taiga-back/issues/128#issue-1688815129
2. https://github.com/raindropio/app/issues/82#issue-1773257937
3. https://github.com/wishlephant/wishlephant-website/issues/1#issue-1782844817
4. https://github.com/bookwyrm-social/bookwyrm/issues/2952#issue-1847099016
5. https://github.com/ValveSoftware/steam-for-linux/issues/10019#issue-1868495803

Acknowledgements

• I have searched the existing issues and this is a new ticket, NOT a duplicate or related to another open issue.
• I have written a short but informative title.
• I will fill out all of the requested information in this form.

Begin with dependent issue #549 and the CalDAV references in this issue to understand the expected integration boundary. Define how the “to watch” and “watched” lists should be exposed, starting with the requested read-only behavior, and establish the acceptance checks for the completed feature.