Support getting encryption context on a message

[BewareMyPower]

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[Copilot]

Pull request overview

This PR adds support for retrieving encryption context from messages in the Pulsar C++ client, enabling applications to inspect encryption metadata and manually decrypt messages when ConsumerCryptoFailureAction::CONSUME is configured. The implementation introduces a new public EncryptionContext class that encapsulates encryption keys, parameters, algorithm, and compression information, along with a flag indicating decryption failure status.

Key changes:

• Introduces EncryptionContext class and EncryptionKey struct as public API types to expose encryption metadata
• Adds Message::getEncryptionContext() method returning std::optional<const EncryptionContext*> to access encryption context
• Refactors MessageCrypto to use EncryptionContext instead of protobuf types for better API abstraction

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
include/pulsar/EncryptionContext.h	New public header defining EncryptionContext and EncryptionKey with methods to access encryption metadata
include/pulsar/Message.h	Adds getEncryptionContext() method and includes <optional> for C++17 support
lib/EncryptionContext.cc	Implementation of EncryptionContext constructor that converts protobuf metadata to public API types
lib/Message.cc	Implements getEncryptionContext() returning pointer to optional encryption context
lib/MessageImpl.h	Adds encryptionContext_ member to store optional encryption context in message implementation
lib/MessageCrypto.h	Updates method signatures to accept EncryptionContext and EncryptionKey instead of protobuf types
lib/MessageCrypto.cc	Refactors decryption methods to work with EncryptionContext API, converting from protobuf field access to method calls
lib/ConsumerImpl.h	Introduces DecryptionResult enum to distinguish between successful decryption, consuming encrypted, and failure states
lib/ConsumerImpl.cc	Creates encryption context before decryption, sets isDecryptionFailed_ flag for consumed encrypted messages, and propagates context to Message
lib/Commands.cc	Propagates encryption context from batched messages to individual deserialized messages
tests/EncryptionTest.cc	New comprehensive test demonstrating manual decryption using encryption context when decryption is disabled
tests/BasicEndToEndTest.cc	Adds assertion to verify encryption context availability and correctness in existing encryption test
win-examples/CMakeLists.txt	Sets C++17 standard required for std::optional support in Windows examples

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