Generate random volumes and densities for items based on the ranges for
those two quantities in the raw when building instances of items.
Since this is the first time creating an item is impure, this also lifts
entity generation into a (random) monadic context
Change-Id: I2de4880e8144f7ff9e1304eb32806ed1d7affa18
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3226
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
I didn't end up using this directly for the thing I was doing, but it
still seems generally useful enough that I'm keeping it around for now
Change-Id: I05c8902d75845f2230ec2373a9677d61cfaafafd
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3206
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
