refactor: extract the methods about user into class User

src/user.ts

@@ -0,0 +1,28 @@
+import * as vscode from 'vscode';
+
+export default class User {
+    private context:vscode.ExtensionContext;
+    private usernameKey:string = 'devstarUsername'
+    private userTokenKey:string = 'devstarUserToken'
+
+    constructor(context: vscode.ExtensionContext) {
+        this.context = context;
+    }
+
+    public getUsernameFromLocal(): string|undefined {
+        return this.context.globalState.get(this.usernameKey);
+    }
+
+    public getUserTokenFromLocal(): string|undefined{
+        return this.context.globalState.get(this.userTokenKey);
+    }
+
+    public setUsernameToLocal(username:string) {
+        this.context.globalState.update(this.usernameKey, username)
+    }
+
+    public setUserTokenToLocal(userToken:string) {
+        this.context.globalState.update(this.userTokenKey, userToken)
+    }
+
+}