微信返回的错误信息：

{ "code":"SIGN_ERROR","detail":{"detail":{"issue":"sign not match"},"field":"signature","location":"authorization","sign_information":{"method":"POST","sign_message_length":173,"truncated_sign_message":"POST\n/v3/merchant/media/upload\n1615867564\n705F23515F6C435FA59BBA631933DAFE\n{\"filena\n","url":"/v3/merchant/media/upload"}},"message":"错误的签名，验签失败"}

这是我拼接的待验签串：

这是拼接body内容