finalize_deepar: Function to select best DeepAR based on chosen metric
In vidarsumo/sumots: Helper functions for Sumo Analytics

Function to select best DeepAR based on chosen metric

finalize_deepar(
  accuracy_table,
  id,
  freq,
  recipe,
  splits,
  epoch,
  metric = "rmse"
)

`accuracy_table`	Table from tune_deepar()
`id`	A quoted column name that tracks the GluonTS FieldName "item_id"
`freq`	A pandas timeseries frequency such as "5min" for 5-minutes or "D" for daily.
`recipe`	GluonTS recipe
`metric`	The metric used to choose the best model
`split`	objects