Add specs for batch assignment (conflict detection), debug batch assignment logic
add #find_obstacles to Assignments Obj, use in batch assignment process
prevent duplicate record error in BatchUpdatable#batch_update
refactor Assignments object -- add assignment wrapping/unwrapping, sort tracking & restoring
debug batch assign logic (fix param passing)
clean up specs
Clean up grid batch assign specs
Add specs for reassigning shifts with conflicts in batch assign routine
Fully flesh out batch assign specs
Add specs for single shift re-assignment using batch routine logic
Clean up RiderShifts to pass batch email specs
Add passing batch email specs
Clean up single assignment email specs
Add specs for emergency shift delegation