[MCO] Add a flag to allow irreconcilable configs

The flag will tell the operator to skip the irreconcilable fields
validation and let the user update/patch conflictive MCs in the cluster
at his own risk. This feature is specially thought to allow users to add
new nodes in a long standing cluster with newer configuration.

Author: pablintino

features.md

@@ -43,6 +43,7 @@
 | MinimumKubeletVersion| | | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span>  |
 | MixedCPUsAllocation| | | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span>  |
 | NodeSwap| | | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span>  |
+| NonReconcilableMC| | | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span>  |
 | NutanixMultiSubnets| | | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span>  |
 | OVNObservability| | | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span>  |
 | PinnedImages| | | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span> | <span style="background-color: #519450">Enabled</span>  |

features/features.go

@@ -30550,6 +30550,10 @@
           "description": "logLevel is an intent based logging for an overall component.  It does not give fine grained control, but it is a simple way to manage coarse grained logging choices that operators have to interpret for their operands.\n\nValid values are: \"Normal\", \"Debug\", \"Trace\", \"TraceAll\". Defaults to \"Normal\".",
           "type": "string"
         },
+        "machineConfigurationValidationPolicy": {
+          "description": "machineConfigurationValidationPolicy tells the operator how new machine configurations should be validated. Allowed values are Strict, Relaxed, and omitted. DefaultValidationPolicy represents a configuration validation mode chosen by the system. Currently, the default is StrictValidationPolicy. StrictValidationPolicy represents a configuration validation mode that enforces that changes to the rendered MCs are not altering fields outside the supported ones. More info about supported fields: https://docs.redhat.com/en/documentation/openshift_container_platform/latest/html/machine_configuration/machine-config-index#what-can-you-change-with-machine-configs RelaxedValidationPolicy represents a configuration validation mode that does not perform any validation over the fields that cannot be changed. Usage of this mode is discouraged.",
+          "type": "string"
+        },
         "managedBootImages": {
           "description": "managedBootImages allows configuration for the management of boot images for machine resources within the cluster. This configuration allows users to select resources that should be updated to the latest boot images during cluster upgrades, ensuring that new machines always boot with the current cluster version's boot image. When omitted, this means no opinion and the platform is left to choose a reasonable default, which is subject to change over time. The default for each machine manager mode is All for GCP and AWS platforms, and None for all other platforms.",
           "default": {},

openapi/generated_openapi/zz_generated.openapi.go

@@ -56,8 +56,42 @@ type MachineConfigurationSpec struct {
 	// +openshift:enable:FeatureGate=NodeDisruptionPolicy
 	// +optional
 	NodeDisruptionPolicy NodeDisruptionPolicyConfig `json:"nodeDisruptionPolicy"`
+
+	// machineConfigurationValidationPolicy tells the operator how new machine configurations should be validated.
+	// Allowed values are Strict, Relaxed, and omitted.
+	// DefaultValidationPolicy represents a configuration validation mode chosen by the system. Currently, the default
+	// is StrictValidationPolicy.
+	// StrictValidationPolicy represents a configuration validation mode that enforces that changes to the rendered
+	// MCs are not altering fields outside the supported ones.
+	// More info about supported fields: https://docs.redhat.com/en/documentation/openshift_container_platform/latest/html/machine_configuration/machine-config-index#what-can-you-change-with-machine-configs
+	// RelaxedValidationPolicy represents a configuration validation mode that does not perform any validation over
+	// the fields that cannot be changed. Usage of this mode is discouraged.
+	// +optional
+	// +openshift:enable:FeatureGate=NonReconcilableMC
+	MachineConfigurationValidationPolicy MachineConfigurationValidationPolicy `json:"machineConfigurationValidationPolicy,omitempty"`
 }
 
+// MachineConfigurationValidationPolicy is the type of validation the MCO applies to incoming MachineConfiguration
+// changes. Allowed values are Strict, Relaxed, and omitted.
+//
+// +kubebuilder:validation:Enum="";Strict;Relaxed
+type MachineConfigurationValidationPolicy string
+
+const (
+	// DefaultValidationPolicy represents a configuration validation mode chosen by the system. Currently, the default
+	// is StrictValidationPolicy.
+	DefaultValidationPolicy MachineConfigurationValidationPolicy = ""
+
+	// StrictValidationPolicy represents a configuration validation mode that enforces that changes to the rendered
+	// MCs are not altering fields outside the supported ones.
+	// More info about supported fields: https://docs.redhat.com/en/documentation/openshift_container_platform/latest/html/machine_configuration/machine-config-index#what-can-you-change-with-machine-configs
+	StrictValidationPolicy MachineConfigurationValidationPolicy = "Strict"
+
+	// RelaxedValidationPolicy represents a configuration validation mode that does not perform any validation over
+	// the fields that cannot be changed. Usage of this mode is discouraged.
+	RelaxedValidationPolicy MachineConfigurationValidationPolicy = "Relaxed"
+)
+
 type MachineConfigurationStatus struct {
 	// observedGeneration is the last generation change you've dealt with
 	// +optional