bootstrap/kubeadm: Add support for Ignition v3.x

implements kubernetes-sigs#9157

bootstrap/kubeadm/api/v1beta1/kubeadmconfig_types.go

@@ -112,6 +112,15 @@ type IgnitionSpec struct {
 	// ContainerLinuxConfig contains CLC specific configuration.
 	// +optional
 	ContainerLinuxConfig *ContainerLinuxConfig `json:"containerLinuxConfig,omitempty"`
+
+	// ButaneConfig contains butane specific configuration.
+	// +optional
+	ButaneConfig *ButaneConfig `json:"butaneConfig,omitempty"`
+
+	// Ignition version, Default to clc
+	// +kubebuilder:validation:Enum=clc;butane
+	// +optional
+	Transpiler string `json:"transpiler,omitempty"`
 }
 
 // ContainerLinuxConfig contains CLC-specific configuration.
@@ -130,6 +139,22 @@ type ContainerLinuxConfig struct {
 	Strict bool `json:"strict,omitempty"`
 }
 
+// ButaneConfig contains butane-specific configuration.
+//
+// We use a structured type here to allow adding additional fields, for example 'version'.
+type ButaneConfig struct {
+	// AdditionalConfig contains additional configuration to be merged with the Ignition
+	// configuration generated by the bootstrapper controller. More info: https://coreos.github.io/ignition/operator-notes/#config-merging
+	//
+	// The data format is documented here: https://kinvolk.io/docs/flatcar-container-linux/latest/provisioning/cl-config/
+	// +optional
+	AdditionalConfig string `json:"additionalConfig,omitempty"`
+
+	// Strict controls if AdditionalConfig should be strictly parsed. If so, warnings are treated as errors.
+	// +optional
+	Strict bool `json:"strict,omitempty"`
+}
+
 // KubeadmConfigStatus defines the observed state of KubeadmConfig.
 type KubeadmConfigStatus struct {
 	// Ready indicates the BootstrapData field is ready to be consumed