fixed missing - on Content-Type

src/app/classes/api-helper.ts

@@ -4,7 +4,7 @@ import { map } from 'rxjs/operators';
 
 export class SoapApiHelper {
     public static call<T>(http: HttpClient, url: string, data: object): Observable<T> {
-        return http.post<T>(url, data, { responseType: 'json', headers: new HttpHeaders({ 'ContentType': 'application/json' }) })
+        return http.post<T>(url, data, { responseType: 'json', headers: new HttpHeaders({ 'Content-Type': 'application/json' }) })
             .pipe(map((response: any) => response.d));
     }
 }