[Feature] Kanban automation using labels

[jwildeboer]

Feature Description

This is an IMHO simpler reformulation of #14359 which should be easier to implement and maintain while giving the kanban/project feature a significant boost in functionality and usability.

Use kanban column names as label for issues

Add a new setting to projects called "Sync kanban with issues". When enabled, it will add a new label to an issue on the kanban. The name of the label should be constructed as PROJECTNAME/COLUMNNAME with the exclusive flag set.

With this very lightweight approach it becomes simple and natural to work with the kanban. As we already have a default column, that's going to be the label for new issues. When an issue is moved between columns, the label is also changed. With this approach no big changes are needed and typical agile patterns in project management can be enabled.

This approach needs no complex rules management, it really boils down to adding/changing/deleting labels on an issue.

On the kanban page this special label doesn't need to be displayed, as it is already reflected by the columns themselves.

On the issue it might be better to make the label protected, to make sure that progress is only managed on the kanban.

Screenshots

No response

[jwildeboer]

Related to #14814 #13498