feat: set_token command

[onx2]

In preparation for bevy_stdb_auth crate, we'll need some way to update the token without causing a reconnect. This exposes a command that will mutate the internal token for use in reconnects later on when needed.

So the general flow is something like:

• Listen for message that the access token has been refreshed from bevy_stdb_auth
• When refreshed, take the token and call set_token with it to update the state

When there is a disconnect + connect for spacetime, this new token will not be expired which means we can safely connect.

fn update_token(stdb_cmds: StdbCmds, msgs: ReadStdbAuthTokenRefreshedMessage) {
  for msg in msgs.read() {
    // new token from the active session... now subsequent reconnects will succeed
    // when the original token would have failed due to expiry.
    stdb_cmds.set_token(msg.session.access_token);
  }

}