Add TLS support about dnp3 HOT 1 CLOSED

dangerous_configuration: this feature enables a dangerous() method on ClientConfig and ServerConfig that allows setting inadvisable options, such as replacing the certificate verification process. Applications requesting this feature should be reviewed carefully.

https://docs.rs/rustls/0.19.0/rustls/trait.ClientCertVerifier.html

This will allow us to work around webpki, although we have to parse and verify certificates ourselves.

A rustls user who had been pushing to enable p2p applications has this crate:

https://crates.io/crates/x509-signature

It parses and verifies signatures, although what I don't like about it is that it doesn't fully parse the cert:

https://docs.rs/x509-signature/0.5.0/src/x509_signature/lib.rs.html#152-296

For example, the issuer and subject fields are not fully parsed!

We could also consider using rasn here and also doing the cert signature verification using ring for the crypto. We don't have to support every type of signature algorithm. we can just choose to support the best / most common ones and document it.

from dnp3.