Improvement: Set due date on created issues

[mrimann]

At the moment, the created JIRA issues do not have a due date set.

For our use-case, it would be helpful to set the due date to a configurable date in the future. As we're using a template for setting some custom fields, it would be cool to be able to configure this per template.

I imagine something in a template like (written out of my head):

[default-workflow]
custom_field = "blubb"
due_date = +3d

This should result in a due date on e.g. Thursday, in case the ticket get's created on Monday.