Upload an attachment

Upload a file (PDF, DOCX, image, etc.) and receive a hashed <code>attachmentId</code>. Pass that <code>attachmentId</code> in the <code>attachmentIds[]</code> of an Email-step variant when creating or updating a step to attach the file to outgoing emails. For attachments referenced from a note, use <code>POST /v1/notes/attachments</code> instead.

<strong>Content-Type</strong>: <code>multipart/form-data</code> with a single <code>file</code> field.