Create a tag

Makes a new segment of this newsletter's audience. Needs audience: write, and is a write.

The tag starts empty. Nobody holds it and no article is addressed to it, so creating one grants nobody access to anything. People are put in it by Apply a tag to a subscriber (POST /subscribers/{subscriber}/tags/{tag}), or by Apply a tag to many subscribers (POST /tags/{tag}/subscribers) for a list, which are the calls that decide access, and an article is addressed to it when it is sent.

name has to be unique among this newsletter's live tags. A name a live tag already has answers 422. A name freed by a retirement is available again, and taking it does not disturb the retired tag, which goes on resolving the audience of the articles it was addressed to.

Publishes no event.