Atomize the metrics models and APIs

Erwan Rouchet
2024-09-30T06:50:30Z

https://redmine.teklia.com/issues/2483#change-55343

Remove the MetricKey and MetricValue models

Move the MetricMode enum to the training.0001 migration

Remove the CreateMetricValue and CreateMetricValues endpoints

You may need to update the test fixtures since they include some Django permissions, even though we don't use those.