test: add another test case to confirm that issue 67 is fixed

[James-4u]

This test verifies that hostname checking on :authority header works correctly
when multiple RPCs with different authority overrides are made on the same channel.

The test demonstrates:

• Valid authorities matching the TLS certificate succeed
• Invalid authorities are rejected with UNAVAILABLE status
• Verification results are cached correctly (LRU cache)
• Each authority is verified independently

I know #67 was fixed already, wanted to add a test case which ensures it's really solved and to close the issue as I thought it's not solved when I was looking at the repo issues.

Contribution by Gittensor, learn more at https://gittensor.io/

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: SmartDever02 / name: aka James4u (7d9cc24)

[James-4u]

@ejona86 requesting your review

[ejona86]

CC @kannanjgithub

Were the tests added in c28a7e3 insufficient? That issue should remain open until we flip GRPC_ENABLE_PER_RPC_AUTHORITY_CHECK to default to true.

[James-4u]

@ejona86 @kannanjgithub thanks for your reply.
btw can you plz let me know if this pr is worth to be merged?

[kannanjgithub]

@SmartDever02 We do already have the unit tests that Eric mentioned in the above comment. Your PR creates a test that

1. Tests using multiple good authorities instead of a single one, but it doesn't add any additional value over the original test that test a good authority and bad authority with the TrustManager separately.

2. Mentions in the comments when the cache is used or not, but does no real assertions as to the number of times the TrustManager verification was invoked. There may be scope to track the counts in HostnameCheckingX509ExtendedTrustManager used by the existing tests and assert it in the tests.