'Message ID' field in git pw series show

[borkmann]

The git pw patch show shows the Message ID field, which is great. When I do a git pw series show, I would love to have the Message ID field as well. In case of a series with a cover letter, that should point to the Message ID of the cover letter, and if the former is not present, then it should point to the first patch in the series. Seems even right now this cannot be scripted since I cannot do git pw patch show <cover-id> if I take the from git pw series show. It would be really useful to have so one can script automated replies.