Add recommendation generation for user range

[joe4dev]

Instead of manually building the recommendations graph for different num_simultaneous_users by triggering many individual recommendation, it should be possible to generate recommendations for an entire user range.

params
ingredient_id The id of the application root ingredient
min
max
step

Example user range
"min"=100
"max"=300
"step"=50

Will generate recommendations for [100, 150, 200, 250, 300] users.