Use MLFLOW_TRACKING_URI environment variable by default instead of mlruns

[Galileo-Galilei]

Description

It is common to specify the mlflow tracking uri through the MLFLOW_TRACKING_URI environment variable. We should have a way to use this variable as the default one in kedro-mlflow

Context

When using kedro-mlflow in a managed cluster where the tracking uri is defined dynamically, I can't use a fixed uri in the mlflow.yml config file.

Possible Implementation

When server.mlflow_tracking_uri is null in mlflow.yml, use MLFLOW_TRACKING_URI instead of mlruns as a default.

kedro-mlflow/kedro_mlflow/config/kedro_mlflow_config.py

Line 18 in fa13573

mlflow_tracking_uri: str = "mlruns"