Missing method 'more-member' of resource 'groups'

[Verhás István]

The StashClient interface in the api module does not define a method to access the 'groups' resource's 'more-member' method. At the REST API, it is documented at https://docs.atlassian.com/bitbucket-server/rest/6.2.0/bitbucket-rest.html#idp10 and it is also working.