Add power display widget

Display/src/app/services/power/power.service.ts

@@ -0,0 +1,28 @@
+import { Injectable } from '@angular/core';
+import { Observable, BehaviorSubject } from 'rxjs';
+import { HubConnectionBuilder, HubConnection } from '@aspnet/signalr';
+import { PowerStatus } from 'src/app/models/power/power-status';
+
+@Injectable({
+    providedIn: 'root'
+})
+export class PowerService {
+    private connection: HubConnection;
+    private latestStatus: BehaviorSubject<PowerStatus> = new BehaviorSubject<PowerStatus>(null);
+
+    constructor() {
+        this.connection = new HubConnectionBuilder()
+            .withUrl('/api/hub/power')
+            .build();
+
+        this.connection.on('LatestSample', (message: string) => {
+            this.latestStatus.next(JSON.parse(message));
+        });
+
+        this.connection.start();
+    }
+
+    getLatestStatus(): Observable<PowerStatus> {
+        return this.latestStatus.asObservable();
+    }
+}