Save the given identity for the given userId, encrypted with the given raw keys.
|The ID of the userId.
|The key under which identity keys are stored. This MUST be a secret known only to this user of your app, and never to other users, as learning it will allow deleting the stored identities. Useful to change if you want to store multiple identities for the same
userId. Allowed characters :
A-Za-z0-9+/=-_@.. Max length is 256 characters.
|The raw encryption key used to encrypt / decrypt the stored identity keys. This MUST be a cryptographically random buffer of 64 bytes.
|The identity to save.