Define a way to handle (semi) private events and cancelled events

[twatzl]

We need a way to handle semi private events.

Sometimes it makes sense to publish the dates for an event where tickets cannot be obtained except for a selected group of people:

• e.g. a railway club might post non public trips for photographers to know.
• this is kind of a special case for the registration tag where the value should be "Private" or "not for sale"

furthermore there is a need for indicating events have been cancelled.

• simply removing them from the list is not a good idea
• changing the name with a prefix would change the idea
• again we could use the registration tag
• possibly other tags as well?

[kadhonn]

could you please split this issue because those are two completely different problems in my opinion

i am torn if we really want such semi-public events on our page

but even if we have them, a tag or something like that should suffice?

for the cancelled events: that is going to be hard, but yes we should think about it
but we have to factor in how the source websites handle it, how we deal with multiple sources, with renames, how we merge events, ...