feat(eventhubs): restore connection string authentication

[Sagar Patel (sagar0207)]

Summary

Restore connection-string authentication for the Event Hubs ProducerClient and ConsumerClient.

The constructors were available through 1.0.0-beta.10 and were removed in 1.0.0-beta.11 during the Rust AMQP merge. The connection-string parser and SAS credential remained, but the Rust backend's token generation and CBS SAS-token handling were incomplete.

Fixes #7250 and #7295.

Azure DevOps work item: 39045651

Supersedes #7293. That PR came from a personal fork, so its CI jobs could not access the internal Azure Rust Cargo feed.

Related earlier draft: #7251.

Changes

• Restored the previous public constructor signatures:

  ProducerClient(
      std::string const& connectionString,
      std::string const& eventHub,
      ProducerClientOptions options = {});
  
  ConsumerClient(
      std::string const& connectionString,
      std::string const& eventHub = {},
      std::string const& consumerGroup = DefaultConsumerGroup,
      ConsumerClientOptions const& options = {});

• Reused ServiceBusSasConnectionStringCredential and the existing uAMQP CBS SAS-token path.

• Added SAS support to the default Rust AMQP backend:

  • Generates HMAC-SHA256 SAS tokens through the Rust wrapper.
  • Matches the existing uAMQP token bytes and URL encoding.
  • Sends servicebus.windows.net:sastoken through the Rust CBS path.
  • Preserves JWT behavior for Microsoft Entra ID credentials.

• Restored EntityPath behavior:

  • An empty Event Hub argument uses the connection string EntityPath.
  • A matching Event Hub argument is accepted.
  • A different Event Hub argument throws std::invalid_argument.
  • An Event Hub name is required when the connection string has no EntityPath.

• Restored Event Hubs emulator support:

  • Uses AMQP without TLS.
  • Defaults to port 5672 when the emulator endpoint has no port.
  • Preserves an explicitly configured non-TLS port.
  • Rejects emulator port 5671 because the current AMQP transport maps that port to TLS.

• Added focused offline tests, a shared fixed-vector token test, and an opt-in live round-trip test.

• Restored and updated four connection-string samples:

  • create_producer.cpp
  • create_consumer.cpp
  • produce_events.cpp
  • consume_events.cpp

• Kept those samples in compile coverage but excluded them from automatic live sample execution because the standard live resources do not expose a connection string.

• Updated the package README with:

  • An inline Microsoft Entra ID example.
  • Connection-string formats with and without EntityPath.
  • Support on both AMQP backends.
  • Current send and receive APIs.

• Updated the samples README and changelog.

Validation

The branch was rebased onto current main at 847ae28b6.

uAMQP

• Event Hubs library built successfully.
• Azure Core AMQP connection-string tests built successfully.
• Event Hubs test executable built successfully.
• All four restored samples compiled and linked successfully.
• The fixed-vector SAS token test passed.
• 13 focused offline connection-string tests passed.
• The live-only test correctly skipped in playback mode.

Event Hubs emulator

The focused round-trip test passed on both uAMQP and Rust AMQP against the Docker Event Hubs emulator using the official connection-string shape without an explicit port.

The test opened the receiver, sent one event, received it, and compared the event body.

Azure Event Hubs

The focused round-trip test passed on both uAMQP and Rust AMQP against:

• Namespace: cpp-connscale-ns
• Event Hub: eh-connscale-testing
• Consumer group: $Default

The connection string was held only in process memory and removed after the test.

Rust AMQP

• Rust SAS token unit tests passed.
• Azure Core AMQP and Event Hubs C++ tests built successfully.
• The fixed-vector test produced the same literal SAS token on both backends.
• 13 focused Event Hubs connection-string tests passed.
• Live Azure Event Hubs and emulator round trips passed.

Scope

This PR does not:

• Change CBS token refresh behavior.
• Change retry or link recovery behavior.
• Change the standard live-test resources to enable local authentication.
• Add a new BlobCheckpointStore constructor.
• Fix the separate Event Hubs performance-test connection-string configuration issue.

Security

• No real connection strings, shared keys, or SAS tokens are stored in the repository.
• Connection-string samples are not automatically executed by the standard live sample job.
• Live SAS validation requires an explicitly supplied SAS-enabled resource.

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[Copilot]

Pull request overview

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Restores connection-string authentication for Event Hubs ProducerClient and ConsumerClient, including SAS token support on the Rust AMQP backend and emulator-specific behavior.

Changes:

• Reintroduced connection-string constructors and EntityPath validation/selection in both clients.
• Implemented SAS token generation + CBS SAS token-type support for the Rust AMQP backend.
• Added offline/live tests and refreshed samples + README/changelog documentation.

Reviewed changes

Copilot reviewed 25 out of 26 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
sdk/eventhubs/azure-messaging-eventhubs/test/ut/connection_string_test.cpp	Adds focused unit + opt-in live round-trip tests for connection-string behavior.
sdk/eventhubs/azure-messaging-eventhubs/test/ut/CMakeLists.txt	Includes the new connection-string unit tests in the test target.
sdk/eventhubs/azure-messaging-eventhubs/src/producer_client.cpp	Restores connection-string constructor logic (EntityPath + emulator port handling).
sdk/eventhubs/azure-messaging-eventhubs/src/consumer_client.cpp	Restores connection-string constructor logic (EntityPath + emulator port handling).
sdk/eventhubs/azure-messaging-eventhubs/samples/produce-events/produce_events.cpp	Adds a connection-string “produce events” sample.
sdk/eventhubs/azure-messaging-eventhubs/samples/produce-events/CMakeLists.txt	Adjusts sample build macro usage; disables automatic run for conn-string sample.
sdk/eventhubs/azure-messaging-eventhubs/samples/consume-events/consume_events.cpp	Adds a connection-string “consume events” sample.
sdk/eventhubs/azure-messaging-eventhubs/samples/consume-events/CMakeLists.txt	Adjusts sample build macro usage; disables automatic run for conn-string sample.
sdk/eventhubs/azure-messaging-eventhubs/samples/basic-operations/create_producer.cpp	Restores a basic connection-string producer sample.
sdk/eventhubs/azure-messaging-eventhubs/samples/basic-operations/create_consumer.cpp	Restores a basic connection-string consumer sample.
sdk/eventhubs/azure-messaging-eventhubs/samples/basic-operations/CMakeLists.txt	Adjusts sample build macro usage; disables automatic run for conn-string samples.
sdk/eventhubs/azure-messaging-eventhubs/samples/README.md	Updates environment variables and sample list naming/descriptions.
sdk/eventhubs/azure-messaging-eventhubs/inc/azure/messaging/eventhubs/producer_client.hpp	Adds public connection-string constructor + docs.
sdk/eventhubs/azure-messaging-eventhubs/inc/azure/messaging/eventhubs/consumer_client.hpp	Adds public connection-string constructor + docs.
sdk/eventhubs/azure-messaging-eventhubs/README.md	Updates auth guidance + modern send/receive examples and conn-string formats.
sdk/eventhubs/azure-messaging-eventhubs/CHANGELOG.md	Records restored connection-string auth + Rust backend support.
sdk/core/azure-core-amqp/test/ut/connection_string_tests.cpp	Adds a fixed-vector SAS token test shared across backends; refactors existing tests.
sdk/core/azure-core-amqp/src/impl/rust_amqp/rust_amqp/rust_wrapper/src/amqp/sas.rs	Implements Rust SAS token generation + percent-encoding compatible with uAMQP.
sdk/core/azure-core-amqp/src/impl/rust_amqp/rust_amqp/rust_wrapper/src/amqp/mod.rs	Exposes the new Rust sas module.
sdk/core/azure-core-amqp/src/impl/rust_amqp/rust_amqp/rust_wrapper/src/amqp/cbs.rs	Extends Rust CBS authorize API to accept token type (JWT vs SAS).
sdk/core/azure-core-amqp/src/impl/rust_amqp/rust_amqp/rust_wrapper/Cargo.toml	Adds Rust crypto dependencies for SAS (base64/hmac/sha2).
sdk/core/azure-core-amqp/src/impl/rust_amqp/amqp/connection_string_credential.cpp	Implements Rust-backend SAS token generation via Rust interop.
sdk/core/azure-core-amqp/src/impl/rust_amqp/amqp/claim_based_security.cpp	Adds SAS token type support for Rust-backend CBS authorize calls.
sdk/core/azure-core-amqp/inc/azure/core/amqp/internal/connection_string_credential.hpp	Adds test-only friend access for fixed-vector SAS token testing.
sdk/core/azure-core-amqp/CHANGELOG.md	Notes Rust backend SAS token generation + CBS token-type behavior.