[Dev] iCalendar UIDs

[Jeffrey Harris]

Hi Folks,

iCalendar vevents and vtodos must have a UID.  RFC 2445 suggests UIDs
look like datestring at host, but UID is just a TEXT value, it's allowed to
be ANY unique text, and the text is case sensitive.

In practice, Apple's iCal just uses UUIDs, similarly Outlook uses a long
hexadecimal string.  For export we can do this, too, but to interoperate
  well I think we need to be able to work with arbitrary UIDs.

Trial balloon:  I'm wondering how crucial it is that we use case
insensitive UUIDs in the repository.  Would it be reasonable to use
arbitrary UIDs instead?  We could continue to use the existing UUID code
to generate UIDs, we'd just allow a wider range of strings to be stuck
into UUIDs.  If we did this, we'd probably want to change the attribute
name to UID.

Alternately, we could just add a UID attribute to Events and Tasks.
Having both a UID and a UUID seems somewhat inelegant, but if we need
to, that's OK, I guess.

Sincerely,
Jeffrey