Check all mandatory Aoc steps in CF importer

[amuolo]

In Import NB parsing of CF, mandatory steps are not retrieved from the dimension but only the CL step is checked.

[tkukuljan]

Additionally there is no error message for the user, when importing the cash flows that do not contain all the mandatory steps.
Should we add it?
@dcolleoni @dtrzesniak @amuolo

[amuolo]

I think we should add an error message in this case. What do you think? @dcolleoni @dtrzesniak

[amuolo]

suppose that a cashflow file is being imported without CL C. At the moment, we have no errors. Wouldn't it be correct to throw an error in the activity log of the importer?