Sends a message to the candidate within their conversation for this position, delivering it directly to the candidate (e.g. by email), and returns the resulting conversation activity record.

body (HTML or plain text) is required; subject and a file attachment may also be included.

Companies created after Jan. 1, 2024 can't message candidates until Breezy verifies them; until then the request is rejected with a 403 and error type companyNotVerified. The company's verified flag is on GET /company/{companyId}.