Expose custom error message for 'must change password'

[evankanderson]

Obviously, there are probably a lot more places where we might want to expose these messages.

We'll also need a new medic release to actually print them, because util.ExitNicelyOnError is called in the CLI.

Sample output:

$ go run ./cmd/cli user get                                              
Error getting personal user: Code: 16
Name: UNAUTHENTICATED
Description: Unauthenticated
Details: password change required

I'm thinking of dialing down the verbosity of ExitNicelyOnError, but that seems separate.

And, for good measure, testing a command that should return a blanked error:

$ go run ./cmd/cli user get --id 1  # as non-root user
Error getting user by id: Code: 7
Name: PERMISSION_DENIED
Description: Permission denied
Details: PermissionDenied indicates the caller does not have permission to
execute the specified operation.

[JAORMX]

Kiitos!

[eleftherias]

There seems to be a pattern in the rest of the code to use GetNiceStatus in this scenario.

[evankanderson]

Good catch! Done!

It turns out that returning NiceStatus instead of *NiceStatus meant that I had to call .String() explicitly later. Now that print call is simpler, too!