fix: use TLS protocol alias to enable TLS 1.3 negotiation

[jetersen]

Problem

SSLContext.getInstance("TLSv1.2") hard-caps TLS negotiation at 1.2. Connections to Vault servers with tls_min_version = "tls13" fail:

javax.net.ssl.SSLHandshakeException: Received fatal alert: protocol_version

fixes #76

Fix

Replace "TLSv1.2" → "TLSv1.3" in three places:

File	Method
rest/Rest.java	DISABLED_SSL_CONTEXT static initializer
SslConfig.java	buildSslContextFromJks()
SslConfig.java	buildSslContextFromPem()

SSLContext.getInstance("TLSv1.3") on Java 11+ (SunJSSE) enables [TLSv1.3, TLSv1.2] by default, which also drops the insecure TLS 1.0/1.1 protocols that "TLS" would otherwise include.

Test

Added testSslContextFromPemSupportsTls13 to SSLTests asserting that SslConfig built with a PEM cert produces an SSLContext supporting both TLSv1.2 and TLSv1.3.

[jetersen]

The test failure in master branch just seems like a container spawn flakey issue, @henryx

[henryx]

Yes, Testcontainers initialization works correctly with Vault 1.x and fails with Vault 2.x, and for this reason I've ignored it for now. In my opinion is not a problem for the purpose of the PR, so I've preferred to merge it and check lately the reason why Vault 2.x doesn't work

[jetersen]

Would a release be possible? @henryx 🙏 🙇

[henryx]

Release published 😉