Updated to angular 11

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

bookie/src/app/taxes/tax.service.ts

@@ -18,7 +18,7 @@ const serviceName = 'TaxService';
 export class TaxService {
   constructor(private http: HttpClient, private log: ErrorLoggerService) {}
 
-  get(id: string): Observable<Tax> {
+  get(id: string | null): Observable<Tax> {
     const getUrl: string = id === null ? url : `${url}/${id}`;
     return <Observable<Tax>>(
       this.http.get<Tax>(getUrl).pipe(catchError(this.log.handleError(serviceName, `get id=${id}`)))