Feature/mssql-big-data-cluster (#4107)

* Adding kubernetes installer.

* Adding variety of kubectl support and integrating into the kubeconfig target cluster page.

* Addressing PR comments, refactored utility file locations and added missing license headers.

extensions/big-data-cluster/src/interfaces.ts

@@ -15,6 +15,25 @@ export enum TargetClusterType {
 	NewAksCluster
 }
 
+export interface Succeeded<T> {
+    readonly succeeded: true;
+    readonly result: T;
+}
+
+export interface Failed {
+    readonly succeeded: false;
+    readonly error: string[];
+}
+
+export type Errorable<T> = Succeeded<T> | Failed;
+
+export function succeeded<T>(e: Errorable<T>): e is Succeeded<T> {
+    return e.succeeded;
+}
+
+export function failed<T>(e: Errorable<T>): e is Failed {
+    return !e.succeeded;
+}
 export interface ClusterPorts {
 	sql: string;
 	knox: string;
@@ -43,4 +62,4 @@ export interface ToolInfo {
 	name: string,
 	description: string,
 	isInstalled: boolean
-}
+}