@interface RLMPermissionUser : RLMObject
A representation of a sync user within the permissions system.
RLMPermissionUser objects are created automatically for each sync user which connects to a Realm, and can also be created manually if you wish to grant permissions to a user which has not yet connected to this Realm.
The unique Realm Object Server user ID string identifying this user. This will have the same value as
@property (assign, readwrite, nonatomic) NSString *_Nonnull identity;