Append sign-off metadata

[rkotze]

Summary

Select any co-author type and append sign-off metadata to the input box.

It should be a secondary option and only be available in the context menu for an item. E.g. right-click on an author and select the sign-off option from the menu.

This should not change the co-author list. e.g. appending sign-off does not move the author into the selected "co-authoring" list.

Example sign-off metadata: Signed-off-by: Random J Developer <random@developer.example.org>

Motivation

Make it easy to append sign-off metadata to a commit message.

Additional context

Stackoverflow info on sign-off metadata.