Clean up loading of Piwind scaling / chunking settings.

[sambles]

Issue Description

The example piwind model stores optional JSON files

• meta-data/chunking_configuration.json
• meta-data/scaling_configuration.json

These are intended to be picked up at by a model registration script (when deployed to a cluster), however that script expects these files to be in the models root directory.

https://github.com/OasisLMF/OasisPlatform/blob/626469d0adeadafa6da3fd5a554cfd24cf08c3fd/kubernetes/charts/oasis-models/resources/model_registration.sh#L14-L15

There is a workaround in the piwind deployment script to copy these from <root>/meta-data/*.json -> <root>/*.json https://github.com/OasisLMF/OasisAzureDeployment/blob/05561827d6ab51d03f1f3095dbe0be86bfe62d01/deploy.sh#L642-L643

Pick a single location and make it consistent.

• [ ] Either files are expected in <root>/meta-data/*.json or <root>/*.json, pick and align all examples to that
• [ ] Update documentation to clarify what these files are, how they are loaded, and where to place them.

[carlfischerjba]

Thanks for logging this. A related improvement would be to allow these paths to be overridden via environment variables. This would allow a bit more flexibility and an easy workaround if some models want to keep these files separate from the model data (which might be a good thing to do anyway).

CHUNKING_CONFIGURATION_FILE="${OASIS_CHUNKING_CONFIGURATION_PATH:-$OASIS_MODEL_DATA_DIRECTORY/chunking_configuration.json}" 
SCALING_CONFIGURATION_FILE="${OASIS_SCALING_CONFIGURATION_PATH:-$OASIS_MODEL_DATA_DIRECTORY/scaling_configuration.json}"