feat: Enable TLS 1.3 with mutual auth (AB:2378)

[shalinnijel2]

Summary of changes:

• Updated create_certs.sh to generate oemCertChain.pem
• Added a new env variable ENABLE_TLS_1_3 - False by default
• Updated get_ssl_context() for server to check client cert chain and client to offer cert chain if TLS 1.3 is enabled
• Updated README.
• Updated .env.dev.local and .env.dev.docker to include ENABLE_TLS_1_3 variable.

[tropxy]

shouldnt it be:

cafile=CertPath.V2G_ROOT_PEM if server_side else CertPath.OEM_ROOT_PEM,

[shalinnijel2]

It looks like caFile points to the certificate required to verify the peer's chain ...
https://docs.python.org/3/library/ssl.html#ssl.create_default_context

[tropxy]

as discussed, the create_default_context already does the same settings as later done in the code; instead we can do the following:

if ENABLE_TLS_1_3:
    ssl_context = SSLContext(protocol=ssl.PROTOCOL_TLS)
else:
    ssl_context = SSLContext(protocol=ssl.PROTOCOL_TLSv1_2)

[shalinnijel2]

Sure, done.

[tropxy]

creating the context without specifying the protocol is deprecated. select ssl.PROTOCOL_TLS instead

[shalinnijel2]

Oops...changed now...