Allow setting certificate common name (DNS name) through a CLI parameter

[murerfel]

Discovered while working for the Ajuna Demo:

For our direct invocation web-socket server, we generate our own certificate at runtime (see here). One requirement to have a valid certificate is that the common name of the certificate matches the DNS name.

So e.g. in case of Ajuna, the worker runs on ajuna-02.cluster.securitee.tech, and the common name of the certificate needs to be set accordingly (by default we set Enclave at the moment, here.
Because this DNS name can change depending on the network topology, it is impractical to have a value hard-coded. Instead, we should add a CLI parameter, so when we start the worker we can provide that common name.

[clangenb]

Absolutely, we should do this ASAP, thanks for the issue!