#2 feat: transparent leader hint reconnect on consume

Summary

• When consume() receives gRPC UNAVAILABLE with x-fila-leader-addr trailing metadata, the SDK transparently creates a new connection to the leader address and retries the consume call once
• Stores TLS/auth configuration in the client to build redirect channels with the same security settings
• Max 1 redirect per consume call to prevent infinite loops

Test plan

• Verify compilation passes (./gradlew compileJava)
• Verify existing tests still pass (./gradlew test)
• Manual test with a multi-node cluster: consume on a follower node should redirect to the leader
• Verify UNAVAILABLE errors without x-fila-leader-addr metadata are still raised as RpcException

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Summary by cubic

Adds transparent leader redirect for consume() when a follower returns gRPC UNAVAILABLE with x-fila-leader-addr. Retries once against the hinted leader, reusing TLS and API key settings.

• New Features

  • On UNAVAILABLE with x-fila-leader-addr, reconnects to the leader and resumes the stream once.
  • Reuses configured TLS (CA, client cert/key) and ApiKeyInterceptor on the redirected channel; extracts channel-building helpers and makes Builder.parseHost/parsePort reusable.
  • UNAVAILABLE without a leader hint still throws the mapped RpcException; CANCELLED exits quietly.

• Bug Fixes

  • Validates leader address hints before redirecting (must be host:port, numeric port 1–65535); invalid hints fail fast.
  • Applied spotless formatting (no behavior change).