* Add S2AStub cleanup handler.
* Give TLS and Cleanup handlers name + update comment.
* Don't add TLS handler twice.
* Don't remove explicitly, since done by fireProtocolNegotiationEvent.
* plumb S2AStub close to handshake end + add integration test.
* close stub when TLS negotiation fails.
* throw IllegalArgumentException in ProtoUtil.
* throw exception in TrustManager in more standard way.
* handle IllegalArgumentException in SslContextFactory.
* Don't throw error on unknown TLS version.
* Combine MtlsToS2ChannelCredentials and S2AChannelCredentials.
* Check if file exists.
* S2AChannelCredentials API requires credentials used for client-s2a channel.
* remove MtlsToS2A library in BUILD.
* Don't check state twice.
* Don't check for file existence in tests.
* Use StandardCharsets in FakeS2AServerTest.
* Use add instead of offer in S2AStub.
* remove dead code in ProtoUtil.java.
* Mark convertTlsProtocolVersion as VisibleForTesting.
* S2AStub doesn't return responses at front of queue.
* Remove global SHARED_RESOURCE_CHANNELS.
* Don't suppress RethrowReflectiveOperationExceptionAsLinkageError.
* Update javadoc.
* Make clear which certs are used in tests + add how to regenerate.
* Mark S2A public APIs as experimental.
* Rename S2AChannelCredentials createBuilder API to newBuilder.
* Remove usage of AdvancedTls.
* Use InsecureChannelCredentials.create instead of Optional.
* Invoke Thread.currentThread().interrupt() in a InterruptedException block.
* S2AHandshakerServiceChannel doesn't use custom event loop.
* use executorPool.
* log when channel not shutdown.
* use a cached threadpool.
* update non-executor version.
Move unused and unimportant fields to local variables. pickUnusedPort()
is inherently racy, so avoid using it when unnecessary. The channel's
default executor is fine to use, but if you don't like it
directExecutor() would be an option too. But blocking stub doesn't even
use the executor for unary RPCs. Thread.join() does not propagate
exceptions from the Thread; it just waits for the thread to exit.
Riya Mehta