Allow Customizable Agent Nodes at Package Level

[lewijacn]

Is your feature request related to a problem? Please describe

As a user of this package, I feel restrained that I cannot control the default Agent Nodes and the way they are initialized at the top CDK level without modifying the underlying package. Defining Agent Nodes seems like a common use case that will vary from setup to setup. Correct me if I'm wrong but it seems the expected way to do this currently is to modify the internal agent-nodes class.

Describe the solution you'd like

I'd like to be able to provide a JSON file path as a prop to the CIStack such that if this optional file path is provided, the CIStack will parse this file to determine what Agent Nodes should be used.

I'd expect basic validation to ensure any required fields for configuring an AgentNode are provided. A possible format for this file below, which is similar to what happens internally:

{
    "agentNodes": [
        {
            "agentType": "unix",
            "customDeviceMapping": "/dev/xvda=:300:true:::encrypted",
            "workerLabelString": "Jenkins-Agent-AL2023-X64-C54xlarge-Single-Host",
            "instanceType": "C54xlarge",
            "remoteUser": "ec2-user",
            "maxTotalUses": -1,
            "minimumNumberOfSpareInstances": 1,
            "numExecutors": 1,
            "amiId": "ami-0d09563cd5663bdc7",
            "initScript": "sudo dnf clean all && sudo rm -rf /var/cache/dnf && sudo dnf repolist && sudo dnf update --releasever=latest --skip-broken --exclude=openssh* --exclude=docker* --exclude=gh* --exclude=python* -y && docker ps",
            "remoteFs": "/var/jenkins"
        }
    ]
}

Describe alternatives you've considered

No response

Additional context

No response

[rishabh6788]

Hi @lewijacn, thank you for creating this issue.
While we try to prioritize this, would really appreciate if you can take a stab at it and raise a PR.
Would be happy to review.

[lewijacn]

Thanks @rishabh6788 will see if I can fit this in, and will update here if I'm able to get started on it. Otherwise, please let me know if someone else is working on this