add CBP get users by group

[paoloromolini]

PR reopened in place of #291
following @JinHuangAtZen comments.

[JinHuangAtZen]

Hi @paoloromolini, I think there is one step missing, which is generate the mock client as mentioned in the readme https://github.com/nukosuke/go-zendesk#to-regenerate-the-mock-client.
After running the go generate ./..., you will see the updated client.go file with the newly added functions. That's why the test fail.

[paoloromolini]

Hi @JinHuangAtZen I got this error when running the command:

go generate ./...                                                                                                                                                                                           [9:14:40]
2023/11/09 09:16:33 Loading input failed: api.go:8:2: unknown embedded interface AppAPI
zendesk/api.go:4: running "mockgen": exit status 1

[JinHuangAtZen]

Hi @JinHuangAtZen I got this error when running the command:

go generate ./...                                                                                                                                                                                           [9:14:40]
2023/11/09 09:16:33 Loading input failed: api.go:8:2: unknown embedded interface AppAPI
zendesk/api.go:4: running "mockgen": exit status 1

Hi @paoloromolini , I've made a new PR with all your changes here #296 and it's passing the tests. I think the issue you see is because this library was recently upgraded to use https://github.com/uber-go/mock, it might not installed in your local dev environment.