Create a bulk timeslot add form

[agrogers]

I want to create timeslots for all teachers in just a few steps. The form should

Allow me to select all the teachers I want. At this point just show the employee selection form
Select the timeslots from a list on the form we want to add to these teachers. All should be selected by default.
The action should not modify any existing timeslots - just add the missing ones.
Report its success or failure in a toast message

[agrogers]

This is not needed now. teacher timeslots are generated dynamically I think. Delete soon.