✨ Introduce v1alpha3 API

[Fedosin]

What this PR does / why we need it:

Introduce v1alpha3 API with Simplified Provider Configuration

Motivation

The v1alpha2 API introduced a ManagerSpec type that abstracted manager configuration (metrics, health probes, leader election, etc.) into a separate structure. While well-intentioned, this approach created unnecessary complexity and reduced flexibility when users needed to configure provider-specific flags. This change simplifies the API by consolidating all provider configuration directly into ContainerSpec.Args, making the API more transparent and easier to understand.

Key Changes

1. Removed ManagerSpec and Related Types

The following types have been removed:

• ManagerSpec - All fields converted to container args
• ControllerManagerConfiguration - Configuration now in args
• ControllerConfigurationSpec - Controller settings now in args
• ControllerMetrics, ControllerHealth, ControllerWebhook - All configuration now in args

2. Simplified AdditionalDeployments

• v1alpha2: map[string]AdditionalDeployments (wrapper struct with Manager + Deployment fields)
• v1alpha3: map[string]DeploymentSpec (direct deployment specifications)

Note: During conversion, ManagerSpec fields in additionalDeployments are not converted to args, as additional deployments are not Cluster API providers.

3. Direct Container Args Configuration

All manager configuration is now specified directly as container arguments:

# v1alpha3
spec:
  deployment:
    containers:
    - name: ""  # Empty name for converted specs
      args:
        "--max-concurrent-reconciles": "10"
        "--v": "2"
        "--feature-gates": "featureA=true"

Instead of the previous structure:

# v1alpha2
spec:
  manager:
    maxConcurrentReconciles: 10
    verbosity: 2
    featureGates:
      FeatureA: true

4. Automatic Conversion

• Bidirectional conversion between v1alpha2 ↔ v1alpha3 is implemented
• v1alpha3 is the new hub and storage version
• Round-trip conversion preserves settings (with noted exception for additionalDeployments manager config)

Benefits

1. Simplicity: Single location for all provider configuration
2. Flexibility: Easy to add custom provider-specific flags without API changes
3. Transparency: Direct mapping to actual container arguments
4. Compatibility: Automatic conversion maintains backward compatibility

Migration

Users can continue using v1alpha2 resources - they will be automatically converted to v1alpha3 internally. A comprehensive migration guide is included in the documentation.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

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[k8s-ci-robot]

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[Fedosin]

/test pull-cluster-api-operator-e2e-main

[k8s-ci-robot]

@Fedosin: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-cluster-api-operator-apidiff-main	af9d074	link	false	/test pull-cluster-api-operator-apidiff-main

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[k8s-ci-robot]

PR needs rebase.

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/lifecycle stale

[furkatgofurov7]

/reopen

[furkatgofurov7]

/remove-lifecycle stale

[furkatgofurov7]

@Fedosin hey, do you have any timeline when this can be picked up back and ready for review?