Support external ID when importing issues
As described in #25799, it can be tedious to reference other issues of the same import in the CSV document. When the document to import was created manually, the order of issues influences the position of rows and therefore the values of parent relations might need to change during the import.
This problem was not only reported in #25799, but also requested by multiple Planio customers.
The proposed patch tries to simplify this use case. It adds a configuration option "Unique ID". When assigning columns of the imported document, the user may select this unique ID column. If so, it will be assumed, that references to other rows will use the unique ID instead of the row position.
N.B.: If that reference starts with a
#, it's still interpreted as existing Redmine ticket ID. Consequently it's not supported to have a unique ID column with values, starting with
This issue is in conflict with #28198. If interested, I'll gladly provide a patch for both features at once.