chore: PQC GAPIC POC

[lqiu96]

[DRAFT]

Branch that showcases the basic PQC support for GAPICs using gRPC and HttpJson. Adds a repro simply to showcase BigQuery using HttpJson with PQC support.

Added README and helper scripts to help with local testing.

[gemini-code-assist]

Code Review

This pull request introduces Post-Quantum Cryptography (PQC) support and verification tools, including a new integration test suite (ITPqc.java) for the GAPIC Showcase server and a standalone BigQuery tracing sample (BqPqcTest.java). Feedback on these changes highlights three critical issues: Conscrypt must be explicitly registered as a security provider in both ITPqc.java and BqPqcTest.java to prevent handshake failures and NoSuchProviderException errors, and the ManagedChannel initialization in ITPqc.java should be wrapped in a try-finally block to prevent resource leaks in case of setup failures.

[gemini-code-assist]

Conscrypt must be registered as a security provider in order to negotiate the hybrid post-quantum key exchange (X25519MLKEM768). Without explicit registration, the tests will fall back to the default JDK provider (SunJSSE) and fail to negotiate the expected PQC group.

Suggested change

	@BeforeAll
	static void setUp() {
	caCertPath = "target/showcase-ca.pem";
	File certFile = new File(caCertPath);
	assertThat(certFile.exists()).isTrue();
	assertThat(certFile.isFile()).isTrue();
	}
	@BeforeAll
	static void setUp() {
	Security.insertProviderAt(Conscrypt.newProvider(), 1);
	caCertPath = "target/showcase-ca.pem";
	File certFile = new File(caCertPath);
	assertThat(certFile.exists()).isTrue();
	assertThat(certFile.isFile()).isTrue();
	}

[gemini-code-assist]

Conscrypt is not registered as a security provider in this standalone verification tool. This will cause SSLContext.getInstance("TLS", "Conscrypt") to throw a NoSuchProviderException when executed. Registering Conscrypt at the start of the main method ensures the provider is available and matches the expected output described in the README.

Suggested change

	public static void main(String[] args) throws Exception {
	System.out.println("[DEBUG] Java Version: " + System.getProperty("java.version"));
	System.out.println("[DEBUG] Java Runtime: " + System.getProperty("java.runtime.version"));
	System.out.println("[DEBUG] Java VM : " + System.getProperty("java.vm.name") + " (" + System.getProperty("java.vm.version") + ")");
	try {
	System.out.println("[DEBUG] Conscrypt Version: " + Conscrypt.version());
	} catch (Throwable t) {
	System.out.println("[DEBUG] Failed to get Conscrypt version: " + t.getMessage());
	}
	public static void main(String[] args) throws Exception {
	System.out.println("[DEBUG] Java Version: " + System.getProperty("java.version"));
	System.out.println("[DEBUG] Java Runtime: " + System.getProperty("java.runtime.version"));
	System.out.println("[DEBUG] Java VM : " + System.getProperty("java.vm.name") + " (" + System.getProperty("java.vm.version") + ")");
	try {
	System.out.println("[DEBUG] Conscrypt Version: " + Conscrypt.version());
	Security.insertProviderAt(Conscrypt.newProvider(), 1);
	System.out.println("Registered Conscrypt provider at position 1.");
	} catch (Throwable t) {
	System.out.println("[DEBUG] Failed to register or get Conscrypt version: " + t.getMessage());
	}