Ask HN: What do you use for SSH key management of teams?

Everyone uses ssh keys to manage access to their servers, but so far I haven't found a great (ideally open) solution to manage those keys.

Manual management is tedious and error prone.

In particular, I want to be able to add and remove keys and assign user's access rights to certain servers.

If I remove a key, the access to all servers should be revoked.

What do you use for this?