Add pre-settled option to consumer

[Gsantomaggio]

This PR adds pre-settled delivery mode support to consumers, enabling "fire-and-forget" or "at-most-once" semantics where messages are automatically settled by the broker without requiring explicit acknowledgment from the consumer. This is implemented through a new PreSettled option in ConsumerOptions.

Changes:

• Introduced IDeliveryContext interface and PreSettledDeliveryContext type that returns errors when settlement methods are called
• Updated AMQP receiver link options to support pre-settled mode with appropriate settlement mode configuration
• Modified test files to use the public Message() accessor method instead of direct field access
• Added comprehensive test coverage and example demonstrating the pre-settled feature
• Updated CI Docker image from RC to stable RabbitMQ 4.2

Closes: #77

[Copilot]

Pull request overview

This PR adds pre-settled delivery mode support to consumers, enabling "fire-and-forget" or "at-most-once" semantics where messages are automatically settled by the broker without requiring explicit acknowledgment from the consumer. This is implemented through a new PreSettled option in ConsumerOptions.

Changes:

• Introduced IDeliveryContext interface and PreSettledDeliveryContext type that returns errors when settlement methods are called
• Updated AMQP receiver link options to support pre-settled mode with appropriate settlement mode configuration
• Modified test files to use the public Message() accessor method instead of direct field access
• Added comprehensive test coverage and example demonstrating the pre-settled feature
• Updated CI Docker image from RC to stable RabbitMQ 4.2

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
pkg/rabbitmqamqp/amqp_types.go	Added preSettled() method to IConsumerOptions interface and implemented it across all consumer option types
pkg/rabbitmqamqp/amqp_utils.go	Modified receiver link creation to configure appropriate settlement modes based on pre-settled option
pkg/rabbitmqamqp/amqp_consumer.go	Added IDeliveryContext interface, PreSettledDeliveryContext type, and logic to return appropriate delivery context based on consumer options
pkg/rabbitmqamqp/responder.go	Updated to use Message() method instead of direct field access for better encapsulation
pkg/rabbitmqamqp/amqp_consumer_test.go	Added comprehensive test for pre-settled mode verifying message consumption and error handling
pkg/rabbitmqamqp/amqp_consumer_stream_test.go	Updated test assertions to use Message() accessor method
docs/examples/pre_settled/pre_settled.go	Added complete example demonstrating pre-settled message consumption
docs/examples/README.md	Added documentation entry for pre-settled example
.ci/ubuntu/gha-setup.sh	Updated Docker image from 4.2-rc to stable 4.2 release

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