Add better error message when user inputs invalid value for environment flag

I recently started to use the Nais CLI. While trying to run nais kafka credentials -t <team> -e dev-gcp --ttl 1d, I encountered an error message:

creating Kafka credentials: input:3:2: createKafkaCredentials The server errored out while processing your request, and we didn't write a suitable error message. You might consider that a bug on our side. Please try again, and if the error persists, contact the Nais team.

The error was caused by the environment flag being set to dev-gcp instead of dev. Running nais kafka grant-access or nais kafka list, however, accepts an environment flag dev-gcp, not dev.

As an easy mistake to make (and detect?), I suggest adding error messages explaining the invalid environment flag in the following cases:

• nais kafka credentials should use -e dev, not -e dev-gcp
• nais kafka grant-access should use -e dev-gcp, not -e dev
• nais kafka list should use -e dev-gcp, not -e dev

Start with the Nais CLI implementations of kafka credentials, kafka grant-access, and kafka list, then trace how each environment flag is validated and how server errors are surfaced. Done means invalid dev/dev-gcp values produce specific guidance for the affected command instead of the generic server error.