Troops must be dropped inside this zone or they won't attack the target.
The zone needs to be drawn in the map so players don't break the flight
plan by accidentally moving the drop waypoint outside the DZ.
I've move the API for doing this out of `PatrollingFlightPlan` in favor
of a mixin so this is no longer presented as `engagement_distance` by
the flight plan. I don't love that it's still the `commit-boundary`
endpoint, but it's fine for now.
I don't know why mypy wasn't able to catch this. pycharm is also
struggling to understand this class.
This isn't actually the data that callers usually want. Most of the
callers just want the bounds. The heading and length are trivially
computed from that. Add a class to contain the result so it's easier to
refactor.
During package planning we don't care about the details of the flight
plan, just the layout (to check if the layout is threatened and we need
escorts). Splitting these will allow us to reduce the amount of work
that must be done in each loop of the planning phase, potentially
caching attempted flight plans between loops.
Split the oversized file into one per plan type. This also moves the
layout responsibility out of the oversized FlightPlanBuilder and into
each flight plan type file.
