Milestone states

Currently milestones can have the following states:

• planning
• open
• locked
• closed

The purpose of planning is that it puts tasks into a 'snooze' state and they aren't shown on the 'next tasks' list for any user. 'locked' milestones cannot have more tasks added to them, and is meant to reflect a milestone which has been fully planned out and is now in progress.

I propose we do away with "planning" as a user definable state and instead introduce a milestone start date which accomplishes the same thing. That is, when in planning (before start date) tasks are effectively in 'snooze' state. The UI will still show "planning" before the start date, so the only change is that the user will not be able to manually set this state. The difference is mainly about not having to remember to change the milestone from planning to open on the right date.

Further, I propose to remove "locked". This state is used to prevent users from adding tasks to a milestone which is already "full". However it is problematic as bugs found in that milestone should still be allowed to be added. Instead we need a new concept showing a user that a milestone is full.

We can show the number of days a milestone is over or under schedule, making it clear whether the milestone still has room. A UI design is still needed for this.