Method for generating random demand: No distribution other than a uniform distribution is possible

Modify the 'generate_random_method' function to allow the definition of a distribution other than the uniform distribution.
The current parameters are valid only for the uniform distribution

Start by locating the generate_random_method function and reading how its current parameters produce a uniform distribution. Define how an alternative distribution should be selected and configured, then verify that existing uniform-distribution behavior remains valid and that the new distribution can generate random demand.

Written by the indexing model from the issue text.