CommandHandler for the RNTO command. Handler logic:
- If the user has not logged in, then reply with 530
- If this command was not preceded by a valid RNFR command, then reply with 503
- If the required TO pathname parameter is missing, then reply with 501
- If the TO pathname parameter does not specify a valid filename, then reply with 553
- If the TO pathname parameter specifies an existing directory, then reply with 553
- If the current user does not have write access to the parent directory, then reply with 553
- Otherwise, rename the file, remove the FROM path stored in the session by the RNFR command, and reply with 250
The supplied pathname may be absolute or relative to the current directory.