missing sched:date attribute

[linuxcaffe]

Describe your issue

taskwarrior has so many date attributes, and sched:date is not currently handled by the app.

Why so many dates? Lemme explain;

due:date is when the task should be completed, often driven by an external motivator, like somebody expecting something. After this date the task is overdue.

sched:date is when the user intends to do a task. This can/ should be before the due:date, so (for example) do it on sched:date and deliver it before due:date. If we want to include sched:date, we'll have to squeeze it into task_edit view.

start:date is intended to act as a marker that the task is IN PROGRESS. taskwarrior can also track start and stop times to show how much time has been spent on a task, but taskwarrior CLI does that solely through the task history function, and the start:date value is cleared on ``task 42 stop", so if we want to track accumulated start/stop times, we'll have to find another method (like creating a start/stop time annotation) Until then a started task should be highlighted, maybe sent to the top of the list, as the task currently in progress. Currently, taskwarrior-flutter assigns a start:date when a task is created, the same as entry:date, and (imho) this a mistake, and when a task is created, the attribute should default to null, unless set by user.

wait:date is a stalling tactic, if you can't do a task right now, you can hide a task from view until wait:date

until:date is when a task will be automatically deleted, as it can not be completed after that date. Think of a task to put out the garbage or buy concert tickets, no point having those tasks listed after that.

end:date is created automatically when a task is completed or deleted. We don't need a UI element to control it, as it's not intended to be user-modifiable.

Would you like to work on this issue?

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[linuxcaffe]

related to #414