Revise double defined carrier attributes

[kndehaan]

Context

Carriers in the ETM have attributes specified that can either be general applicable to the carrier or can be dataset-dependent that will be read from a dataset's the carriers.csv file.

Current shortcoming

Within the Added direct emissions project, for some carriers the attribute co2_conversion_per_mj has been set to zero on the carrier itself (for example ambient_cold). At the same time, some of these carriers are also present in the carriers.csv file and therefore have a field co2_conversion_per_mj in there, meaning that a value for this attribute could be present there. The result is that the value of the attribute is double defined for some carriers.

Proposed enhancement

The double defined carrier attributes need to be reviewed and solved. This ties into a bigger desire to revise how carriers and the carriers.csv file should be defined.

Success criteria

The value of a carrier attributes is not double defined but has a single source of truth.

Might be picked up in theme Calculation model in a carrier or cleanup project.