eis: Add API to add client getting an fd
Creates the socket and adds it; is intended to be used to create client connections that are passed via a secure channel, e.g. via portals.
Signed-off-by: Jonas Ådahl jadahl@gmail.com
Something we want? I found it a bit "busy" to have to deal with a very particular type of socket fd that libei expected, so maybe we can hide that behind an API?