Changes to Send a campaign immediately

added the media type application/json for the response with the status 403

added the non-success response with the status 429

added the optional property lists to the response with the 200 status

added the optional property reply_to_email to the response with the 200 status

added the optional property is_web_gated to the response with the 200 status

added the optional property preview_text to the response with the 200 status