CLI docs don't specify that to create a token you need a username

I was testing the CLI to create an authentication token, following the docs in https://docs.influxdata.com/influxdb/cloud/security/tokens/create-token/#create-a-token-using-the-influx-cli and https://docs.influxdata.com/influxdb/cloud/reference/cli/influx/auth/create/

I kept getting an error:
`Error: could not find user with name "": %!w().`

It turns out that you have to provide a username:
`influx authorization create --read-buckets --org-id 8ebf5208251c5eb3 -u wbaker@influxdata.com`
but I didn't see anything in the docs that indicated that, and it wasn't included in any of the examples.

Start with the linked token-creation and `influx auth create` documentation pages. Update the guidance and examples to state that a username is required and show the `-u` option; the work is done when users can find that requirement before running the command.

Written by the indexing model from the issue text.