add specs for Shift#batch_create
Add specs for #batch_edit_shift and #batch_edit_assignment from shift index
add specs for #batch_assign from shift grid
Add specs for RiderMailer#delegation_email
refactor delegation_email -- pull helpers into separate class, add conditional forks for staffers and email type
Add specs for batch delegation email
Move batch assignment logic from Shifts controller to Assignments controller
some stuff
clean up specs
Add Assignments#send_batch_emails and RiderShifts concern class
Tweak #batch_update to pass email specs
add Grid#send_emails