Setting subject and email address for NSSharingServiceNameComposeEmail via private API

gistfile1.m

NSSharingService *service = [NSSharingService sharingServiceNamed:NSSharingServiceNameComposeEmail];
NSDictionary *parameters = @{
    @"NSSharingServiceParametersDefaultSubjectKey": @"Lo, a subject!",
    @"NSSharingServiceParametersDefaultRecipientsKey": @[@"someone@somewhere.com"]
};
[service setValue:parameters forKey:@"parameters"];
[service performWithItems:@[@"Woo, private API."]];