Implement ed25519 certificates support for sftp external storage

Implement ed25519 certificates support for sftp external storage: I currently manage several nextcloud v19 and v18 distributions on which I have activated the module for storing external folders, and often I find myself managing this module with rsa key authentication, it is possible to also give it authentication with public / private signature certificates also with elliptic curve certificates see keys ed25519? currently, as can also be seen from the attached authentication via sftp, it is possible only by using private or public key rsa non ed25519 or ecdsa