Add check that all headers specified by @ExcelCellName are present.

[Brutus5000]

Configurable by a new flag in the PoijiOptions, disabled by default.

[ozlerhakan]

could you elaborate more about the option? and please make an example on readme.adoc if necessary

[Brutus5000]

The underlying problem: If you add a field to your model referenced by name via @ExcelCellName, all values will be set to null if the column is missing. If the value is allowed to be null, you can't distinguish between "the user forgot to add the column" and "the user wants to set the value to null".

This can lead to unintentional data loss if
a) the user accidentially deletes or renames a column
b) you add columns to your data model after go live.

In our case it's due to backwards compatibility:
We use Poiji to import bulk patches to master data. Now the user has an existing import file and prepared some changes. At some point in time we add a new nullable field that already exists in the api for a longer time. If the user now imports his "old" format without the new colum, Poiji will parse the old file without errors, but the import will set all values of the new field with null override all existing values of the new column.

I will add an example to the docs.

[ozlerhakan]

thanks @Brutus5000 , it will be ready on 2.7.0