I am trying to set a new header on every http response so the response includes a content-security-policy using the latest version of angular. I have created this http interceptor, and when I go to add to the header I don't get any errors or anything, but nothing actually gets added to the response headers. Here is the code I have for the interceptor. Is there anything that I should change here, or is it not possible to add response headers to every http response from angular.

  HttpEvent,
  HttpInterceptor,
  HttpHandler,
  HttpRequest,
  HttpResponse,
} from '@angular/common/http';
import { Injectable } from '@angular/core';
import { Observable } from 'rxjs';
import { filter, map, tap } from 'rxjs/operators';

@Injectable()
export class AddHeaderInterceptor implements HttpInterceptor {

    intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {

      return next.handle(req).pipe(
        filter(event => event instanceof HttpResponse),
        tap((event: HttpResponse<any>) => {
          event.headers.append('content-security-policy', 'some content-security-policy')
        })
      );
      }
    }