Repository.Token() generates a base64-encoded token that can
be stored in password manager that fully describes repository connection
information (blob.ConnectionInfo) and optionally a password.
Use `kopia repo status -t` to print the token.
Use `kopia repo status -t -s` to print the token that also includes
repository password.
Use `kopia repo connect from-config --token T` to reconnect using the
token.
completely rewrote password storage:
- by default passwords are kept in OS-specific keyring (Keychain on macOS,
Windows Credentials Manager on Windows), which can be optionally disabled
to store password in a local file.
- on Linux keychain is disabled by default (does not work reliably
in terminal sessions), but can be enabled using command-line flag.
