- Add `overrides` field to `rem` type to hold single-event REMs from
non-cancelled overrides
- Add `is_cancelled`, `build_override_rem`, and `collect_overrides` to
process RECURRENCE-ID override events
- Replace `warn_unhandled_recurring` with `collect_overrides` in the
collector pipeline
- Fix `separate_master_and_recurrence` partition logic (swapped
`Left`/`Right`)
- Render override REMs appended to the master REM in `string_of_rem`
Paolo Donadeo
c246ec6775