Add a Prefix field to core.GenericEtl._load

[Sun-flow]

Is your feature request related to a problem? Please describe.
the core.GenericEtl._load() function lacks the ability to specify a prefix when saving a model. Currently, all calls to GenericEtl.load() which include an output location will result in saving a file in the specified output location a name in the format of {model_name}.json

Describe the solution you'd like
I would like to add a field to the _load() function that allows a user to specify a prefix for the saved asset, such as {Subject_ID}, so that output files do not need to be manually renamed if users want to generate multiple models in the same location.

[jtyoung84]

@mekhlakapoor Can you move this to a Discussion?