Add OIDC Client SPI

[sberyozkin]

Fixes #42878

[sberyozkin]

I know we are supposed to try to close smaller issues, but I'd like to make sure we have a good support in LTS for the forthcoming Mailer XOAuth2 work...

[github-actions]

🙈 The PR is closed and the preview is expired.

[quarkus-bot]

Status for workflow Quarkus Documentation CI

This is the status report for running Quarkus Documentation CI on commit 00db230.

✅ The latest workflow run for the pull request has completed successfully.

It should be safe to merge provided you have a look at the other checks in the summary.

Warning

There are other workflow runs running, you probably need to wait for their status before merging.

[quarkus-bot]

Status for workflow Quarkus CI

This is the status report for running Quarkus CI on commit 00db230.

✅ The latest workflow run for the pull request has completed successfully.

It should be safe to merge provided you have a look at the other checks in the summary.

You can consult the Develocity build scans.

---

Flaky tests - Develocity

⚙️ JVM Tests - JDK 21

📦 integration-tests/virtual-threads/grpc-virtual-threads

✖ io.quarkus.grpc.example.streaming.VertxVirtualThreadTest.testStreamingOutputCall - History

• INTERNAL: Half-closed without a request - io.grpc.StatusRuntimeException

io.grpc.StatusRuntimeException: INTERNAL: Half-closed without a request
	at io.grpc.Status.asRuntimeException(Status.java:533)
	at io.grpc.stub.ClientCalls$BlockingResponseStream.hasNext(ClientCalls.java:631)
	at java.base/java.util.Iterator.forEachRemaining(Iterator.java:132)
	at io.quarkus.grpc.example.streaming.VirtualThreadTestBase.testStreamingOutputCall(VirtualThreadTestBase.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at io.quarkus.test.junit.QuarkusTestExtension.runExtensionMethod(QuarkusTestExtension.java:973)
	at io.quarkus.test.junit.QuarkusTestExtension.interceptTestMethod(QuarkusTestExtension.java:823)

[sberyozkin]

Let me merge as this PR has got 2 approvals, Michal, @michalvavrik, ping me please if you'd like to add anything

[michalvavrik]

I think this makes sense. LGTM