Creates a GroupQuery that allows to programmatically query the groups.
Creates a UserQuery that allows to programmatically query the users.
Deletes the group. When no group exists with the given id, this operation is
Delete the membership of the user in the group. When the group or user don't
exist or when the user
Creates a new group. The group is transient and must be saved using
Saves the group. If the group already existed, the group is updated.
Creates a new user. The user is transient and must be saved using
Saves the user. If the user already existed, the user is updated except user
password. Use #updateUs
Update user password. Use #saveUser(User) for new user.
Checks if the password is valid for the given user. Arguments userId and
password are nullsafe.