Allow admin to input start and end time for slot config instead of number of slots
Suggestion by reviewer at Reinier de Graaf
Summary
It's difficult to compute off the top of your head how many slots you need if you want to make slots for a certain time period. Instead of forcing users to compute this, we should swap their num. slots input with a "end time" input. On the backend, we can then compute the number of slots needed to fill the time between start and end time with the given slot lengths and transition lengths.
Reasoning
It's simply much easier to say: "From 2 to 4pm, we're open to visitors", than to compute the number of slots needed for that.