TODO file for DateTime::Incomplete

- more tests for next/previous/closest with year and nanosecond
- use $FIELDS[0] instead of 'year'; $FIELDS[-2] instead of nanosecond
- change @FIELDS to a "class" constant (instead of "package")

- "truncate" tests

- locale and time_zone tests:

  mixing string and object time_zones

  time_zone-only and locale-only DT::I objects

- DT::Set needs a fix to avoid generating big in-memory sets,
  when the result of an operation is a finite set.
  (see SKIP in t/02incomplete.t)

IDEAS

* add_datetime

Just like to_datetime, but adds the field values.

* compare

or is that simply not defined?

* join( $dti )

join the "defined" keys of two DT::Incomplete objects

* keys or defined_fields

returns a list of names of "defined" fields

* to_spanset

* to_span

* other C<DateTime> methods (strftime, locale ... )

* set_week

$dti->set( week => 10 )

* from_datetime / today / now

* truncate

* to_recurrence( resolution => 'days' )

Generates a recurrence of such 'density' (now it always defaults to seconds)

* is_incomplete/is_complete

How do we know it is complete?

