set_security: Enable io.RawIOBase as an alternative to a string-based path to the certificates

[parallaxe]

In cases where the certificates are only in-memory or not explicitly stored inside a file, it is a bit cumbersome to create a temporary file just to call set_security.
My suggestion is to add io.RawIOBase as another alternative for certificate, private_key and server_certificate.

Any opinions on that? If you think this is worthwhile, I would start implementing it as soon as possible.

[oroulet]

No problem