v0.13.9: @newsroom.writer: the user keeps the meter

The user keeps the meter: a proposed design for user management, activity and billing on the client, with vaults.

• One billing vault per user. The user's browser appends its activity, signed by the user; the admin side commits credit, signed by the admin key.
• Stripe from the admin's browser. Payments are listed and matched to signed claims, since webhooks need a public server.
• One light check at the server. The upload server checks a valid key and a cached, signed credit through a small credits API.
• Four parties. The admin vault, the user, the upload server and the credits API.
• Open questions. When a payment counts, who creates the first vault, and how refunds are written.
• Two diagrams. Drawn in Mermaid, with their source in the article.
• The list of articles to write now includes one on the versioned API sites.