Add Header using Interceptor on every http client request

add-header.interceptor.ts

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

@Injectable()
export class AddHeaderInterceptor implements HttpInterceptor {

  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    console.log(`AddHeaderInterceptor - ${req.url}`);
    
    let jsonReq: HttpRequest<any> = req.clone({
      setHeaders: {'Content-Type': 'application/json'}
    });
    
    return next.handle(jsonReq);
  }

}

/*
Configure interceptor in module
...
import { NgModule, Optional, SkipSelf, ErrorHandler } from '@angular/core';
import { CommonModule } from '@angular/common';
import { HTTP_INTERCEPTORS } from '@angular/common/http';
import { AddHeaderInterceptor } from './add-header.interceptor';
...
...
@NgModule({
  imports: [
    CommonModule
  ],
  declarations: [],
  providers: [
    LoggerService, 
    DataService, 
    { provide: HTTP_INTERCEPTORS, useClass: AddHeaderInterceptor, multi: true },
...

*/