Create a collection

Creates a collection in the website’s CMS. slug uses lowercase letters, digits, and hyphens (max 64 characters, starting with a letter) and must be unique among the website’s active collections; displayName is 1–200 characters and description up to 2,000. Optionally pass fields (up to 100, same shape as the create-field body) to define the schema in the same call. A website can hold at most 100 active collections; the limit is enforced with a conflict error.