Add support for Launch Templates, custom AMI and more features for Managed Nodegroups

[cPu1]

Description

Adds launch template support for managed nodegroups. Also adds support for the following features for managed nodegroups:

• Custom AMI (ami)
• instancePrefix and instanceName to configure the EC2 instance name for a nodegroup
• securityGroups.attachIDs to add custom security groups
• ebsOptimized, volumeType, volumeName, volumeEncrypted, volumeKmsKeyID and volumeIOPS
• maxPodsPerNode
• preBootstrapCommands and overrideBootstrapCommand
• disableIMDSv1

To use the launch templates features, specify an existing launch template:

apiVersion: eksctl.io/v1alpha5
kind: ClusterConfig
metadata:
  name: cluster
  region: us-west-2
managedNodeGroups:
- name: launch-template-ng
  launchTemplate:
    id: lt-<id>
    version: "1" # (optional) defaults to the default launch template version

TODO:

• Add documentation

Closes #2551

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the userdocs directory)
• Manually tested
• Added labels for change area (e.g. area/nodegroup), target version (e.g. version/0.12.0) and kind (e.g. kind/improvement)
• Make sure the title of the PR is a good description that can go into the release notes

[michaelbeaumont]

Am I reading this correctly that the tests unmarshal and marshal and then compare the json? Why not match on the structs?

[cPu1]

That's right. The unmarshalling (goformation.ParseJSON(bytes)) and marshalling is actually testing goformation's ability to preserve isomorphism, to ensure no types or values are lost or are interpreted differently.

Why not match on the structs?

Matching on the structs will require more code than matching on the expected JSON output. This is also close to an end-to-end test.

[michaelbeaumont]

makes sense!

[michaelbeaumont]

😯 What's the difference?

[cPu1]

The methods in require stop the test (calling FailNow) when an assertion fails.

[michaelbeaumont]

ah ok so probably it should always be require 👍

[michaelbeaumont]

Can we also add some integration tests?

[cPu1]

Can we also add some integration tests?

I was planning to but couldn't get to it. I'll address it in a separate PR. WDYT?

[kkl-acies]

Did this PR remove the network interface from the created launch template? If yes why?