Changes proposed in this Pull Request

When using distributed generators, nodal fractions should be computed on the bus level. But currently, nodal fraction was not taking into account the fact that the bus level was not the same as the generators locations. Hence a grouby need to fix that.

Checklist

• I tested my contribution locally and it seems to work fine.
• Code and workflow changes are sufficiently documented.
• Changed dependencies are added to envs/environment.yaml.
• Changes in configuration options are added in all of config.default.yaml.
• Changes in configuration options are also documented in doc/configtables/*.csv.
• A release note doc/release_notes.rst is added.