Hello, our team is new to ORY. We are doing some research and have some initial questions. We would like for any user to bring their existing identity (MS, Google, GitHub) or register a manual credentials set through Kratos. How can we do this? We then use Hydra on top of our existing applications at different URLs to route users back to log in, and pick up the identity of their choice from Kratos. The concept of allowing admins to manage identities in their group and manually create or invite members seems to be missing. Also, how could Keto help integrate with things like group permissions?