Constructs a 301 Moved Permanently response.
This indicates that the requested resource has moved permanently to a new
URI. location is that URI; it can be either a String or a Uri. It's
automatically set as the Location header in headers.
body is the response body. It may be either a String, a
Stream, or null to indicate no body. If it's a String,
encoding is used to encode it to a Stream. It defaults to
UTF-8.
If encoding is passed, the "encoding" field of the Content-Type header
in headers will be set appropriately. If there is no existing
Content-Type header, it will be set to "application/octet-stream".
Source
Response.movedPermanently(location, {body, Map<String, String> headers,
Encoding encoding, Map<String, Object> context})
: this._redirect(301, location, body, headers, encoding,
context: context);