Dont use non-standard characters in cookie names

[fogine]

Is your feature request related to a problem? Please describe.

This module should not use non-standard cookie names. It should use alphabetical characters only so its simple to use in established programs like nginx.

Describe the solution you'd like to see

change cookie names eg. from auth._token.local to -> auth_token_local

Describe alternatives you've considered

As far as I know its currently possible to change prefix auth. to auth_ via auth.cookie.prefix in nuxt.config but it still adds .local to the cookie name..