Support date-only poll options

⚠️ This issue respects the following points: ⚠️

• I agree to follow Nextcloud's Code of Conduct.

Describe the goal you'd like to achieve

As a poll owner, I want to be able to suggest date-only options (without timing) because it allows for flexible scheduling, e.g. agreeing to meet in the evening on a certain date without agreeing to the exact time.

This was requested earlier here: #2290

Many thanks for a great product!!

Describe possible solutions

No response

Additional context

The issue today is that an all day event is displayed as bridging two different dates, which is confusing, because it looks like a two-day event is proposed. I hope the attached screenshots of poll visitor (first screenshot) and poll creator (second screenshot) display how unintuitive this is currently.

I believe the following issue is also related: #2368

[github-actions]

This issue is marked as stale, because it had no activity in the last 30 days. It will be closed in 5 days.

[andreas-1107]

I would really appreciate this as well. I first thought it was fixed but it seems it only appears as a full day event correctly when user is in the same time zone as the event creator. (Also there is no way to set time zone, which adds to the complication.)

[dartcafe]

I linked the timezone PR, because it also may cover possible confusion, if the participant resides in another timezone.

Day only events seem to keep a day long duration, because it may be unclear for a participant in another location to understand, which date actually is meant, if date borders are crossed between the owner and the participant.

In this case the participant will get the hint about the different timezones and is able to chose the view.

Annotations and discussion are welcome in the PR #4437 to bundle all comments.