Proposed Changes

This PR adds support for multiple hostname paths in the AWS peer discovery plugin to enable zero-downtime rolling upgrades during hostname migration scenarios. The implementation allows RabbitMQ nodes to discover peers using multiple hostname paths, ensuring cluster formation succeeds even when nodes are configured with different hostname paths during rolling upgrades.

Backward Compatibility

Existing single hostname_path configuration continues to work (unchanged).
We fallback to single path behavior when no numbered paths are configured.

Configuration Examples

Multiple paths for zero-downtime migration

cluster_formation.aws.hostname_path.1 = networkInterfaceSet,2,privateIpAddressesSet,1,privateDnsName
cluster_formation.aws.hostname_path.2 = privateDnsName
cluster_formation.aws.hostname_path.3 = networkInterfaceSet,1,privateIpAddressesSet,2,privateIpAddress

Note: This follows the existing pattern we have for classic_config:

cluster_formation.classic_config.nodes.1 = rabbit@<hostnameA>
cluster_formation.classic_config.nodes.2 = rabbit@<hostnameB>
cluster_formation.classic_config.nodes.3 = rabbit@<hostnameC>

Single path (backward compatible)

cluster_formation.aws.hostname_path = privateDnsName

Types of Changes

What types of changes does your code introduce to this project?
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• Bug fix (non-breaking change which fixes issue #NNNN)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause an observable behavior change in existing systems)
• Documentation improvements (corrections, new content, etc)
• Cosmetic change (whitespace, formatting, etc)
• Build system and/or CI

Checklist

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• Mandatory: I (or my employer/client) have have signed the CA (see https://github.com/rabbitmq/cla)
• I have read the CONTRIBUTING.md document
• I have added tests that prove my fix is effective or that my feature works
• All tests pass locally with my changes
• If relevant, I have added necessary documentation to https://github.com/rabbitmq/rabbitmq-website
• If relevant, I have added this change to the first version(s) in release-notes that I expect to introduce it