Create a DRAFT listing on Capmus on the poster's behalf. Any email is accepted — never ask the user to qualify first. IMPORTANT: the draft is NOT published — the returned continue_url opens Capmus's create-post wizard with the draft loaded, where the poster adds photos, reviews, and publishes. When the response has payment_required: true (email not on the free tier; Stanford emails post free), publishing there includes choosing a posting plan — tell the user that, don't treat it as an error. Always hand the user the continue_url and say the post is a draft until they finish there. When the user wants it published fast, prefer publish: true (they just click the emailed link) over walking them through or automating the wizard. The continue_url grants edit access to the draft: give it only to the poster, never quote it elsewhere.
ConnectorNo auth