'IS NULL' and default value are not added when extra source columns are migrated #1908
Description
migration.pl supports the feature that extra columns from the source database are also migrated to the target database. These extra columns should have the same name and the same data type as the source columns. But it looks like this does not work for 'IS NULL'. The reason is that in e.g. in https://github.com/RotherOSS/otobo/blob/rel-10_1/Kernel/System/MigrateFromOTRS/CloneDB/Driver/mysql.pm#L296 the check is $ColumnInfos{IS_NULLABLE} =~ /no/ while IS_NULLABLE is either NO or YES.