Implement close action with v2 hooks using a finalizer (#80)

* Implement close action with v2 hooks using a finalizer

* Rename cancel to close as we not canceling preparation, just
  notifying that the node disruption has ended.

* For each impacted budget of a node disruption we are calling
  the associated application disruption budget Close hook.

Author: jeremy-clerc

api/v1alpha1/nodedisruption_types.go

@@ -101,8 +101,10 @@ type NodeDisruptionStatus struct {
 type DisruptedBudgetStatus struct {
 	Reference NamespacedName `json:"reference,omitempty"`
 	Reason    string         `json:"reason"`
-	Preparing bool           `json:"preparing"`
-	Ok        bool           `json:"ok"`
+	// Preparing is set to true when the application manager started preparation. Value is kept true even when the app is ready.
+	Preparing bool `json:"preparing"`
+	// Ok is set to true when application manager preparation is complete and ready for the NodeDisruption to continue.
+	Ok bool `json:"ok"`
 }
 
 //+kubebuilder:object:root=true

app_manager_openapi.yml

@@ -128,10 +128,10 @@ paths:
           $ref: '#/responses/RetryAfter'
         default: 
           $ref: '#/responses/UnexpectedError'
-  /cancel:
+  /close:
     post:
-      summary: Cancel application preparation for a disruption.
-      operationId: cancelPreparation
+      summary: Notify the end of a disruption if the application needs to unprepare.
+      operationId: closeDisruption
       tags:
         - disruption
       consumes: