Add the ability to provide _CMD environment variables the same way you can use _cmd options in the configuration. Those _CMD environment variable would have priority against the _cmd options the same way the usual environment variables have priority against the configuration options.
The goal is to allow Kubernetes users to provide such commands via configmap, and reference them in the configuration using environment variables. The referenced script would itself consume secrets in order to construct the connection.
For exemple a script provided as a configmap and referenced by AIRFLOW_CORE_SQL_ALCHEMY_CONN_CMD would compute the Alchemy connection using the database user and password provided as secrets:
echo -n "postgresql+psycopg2://`cat /var/run/secrets/postgresql/postgresql-user`:`cat /var/run/secrets/postgresql/postgresql-password`@$POSTGRESQL_SERVICE_HOST:$POSTGRESQL_SERVICE_PORT/airflow"