def card(header, sections)
      payload = { cards: [header: header, sections: sections] }
      send_request(payload)
    end
def card(header, sections)
      payload = { cards: [header: header, sections: sections] }
      send_request(payload)
    end
Sends Card Message
 @since 0.0.4
 @param header [Hash] card header content
 @param sections [Array<Hash>] card widgets array
 @return [Net::HTTPResponse] response object