* Add Impersonation Tokens Support and Add missing field to CreateGroupOptions

* Fix ImpersonationToken Example

* Add comment again that was mistakenly deleted

* Fix CreateImpersonationTokenOptions

Fix CreateImpersonationTokenOptions for ExpiresAt can be empty

* Update impersonation.go

* Remove not existent option field

* Fix pointers and insert 'omitempty'

* Update documentation links

* Adjust review considerations