…block if missing

In Odoo, as soon as lot_name field and expiration_date one are filled in,
lot will be created from those values if it does not exists. We should
inform user that the line is ready and has all the information in that case.

…piraton date

The set_lot method is quite complex and had multi purpose. It's called
multiple times by the JS code to fill the lot name and the expiration date.
Each call is independent and the method must handle all the cases. That's
mean the method must take care of the previous values provided by the user
at each call and ensure that the couple lot name/expiration date is valid.

Before this change, if a first call was done with a lot name, an existing lot
or a new one was linked to the move line. Then if a second call was done with
an expiration date, the method updated the existing lot with the new
expiration date. This could lead to inconsistencies if an existing lot
already linked to quant packages was updated with a different expiration date.
In addition, if the user changed the lot name on a new call, a new lot
was created even if the previous created lot was not used.

To void these issues, the implementation has been changed to never created
or update an existing lot and detect which parameter has explicitly been
provided by the user.

In any case, the couple lot name/expiration are checked to ensure they are
consistent. We detect if an existing lot could conflict with the provided
values. At the same time, at first call, if a lot is found for the provided
lot name and/or expiration date, we fill the missing value to help the user.

As result, a main change is that the lot is now created when the line
is validated.

Ensures that the value entered into the UI is properly converted into UTC according to the warehouse timezone