Evaluate d_prep for the last assimilation
Description
Add a boolean in the input to indicate whether to perform the forecast step for the last assimilation: is_forecast_for_last_assimilation
. The default will be true.
Motivation
When solving the optimization problem, the current implementation does not perform the forecast step. For example, a unique assimilation step, a forecast d0 is obtained from an ensemble m0. Then the assimilation produces a new ensemble m1, but so far d1 is not computed.