Updated to angular 11

Now compiling with strict mode in typescript
Need to error checking now

bookie/src/app/product/product.service.ts

@@ -17,7 +17,7 @@ const serviceName = 'ProductService';
 export class ProductService {
   constructor(private http: HttpClient, private log: ErrorLoggerService) {}
 
-  get(id: string): Observable<Product> {
+  get(id: string | null): Observable<Product> {
     const getUrl: string = id === null ? `${url}` : `${url}/${id}`;
     return <Observable<Product>>(
       this.http