check username and apikey are registered on OGS before displaying a "Connected"

[wonderingabout]

currently if i use --username woof --apikey woofwoof we still connect successfully

this username and apikey do not exist on ogs though, so in case bot admin enters typoed username/ apikey, or just in case of misuse, it would be good to add a check for that and throw an error instead of connecting, which will generate other errors later anyways