title: RequestOptions deprecated symbol error in Angular 5
body: <p>I'm trying to adapt code in Angular 4 to Angular 5.
  I made many changes but I had an error about <code>RequestOptions</code>.
  The code is about authentication and this is where I have the error:</p>
  <pre class="lang-js prettyprint-override"><code>import { Injectable } from '@angular/core';
  import { RequestOptions } from '@angular/http';
  import { User } from '../model/model.user';
  import 'rxjs/add/operator/map';
  import { HttpClient, HttpHeaders } from '@angular/common/http';
  
  @Injectable()
  export class AuthService {
      constructor(public http: HttpClient) { }
  
      public logIn(user: User) {
  
          const headers = new HttpHeaders();
          headers.append('Accept', 'application/json')
          // creating base64 encoded String from user name and password
          const base64Credential: string = btoa(user.username + ':' + user.password);
          headers.append('Authorization', 'Basic ' + base64Credential);
          // this is where i'm having a problem : 
          const httpOptions = new RequestOptions();
          httpOptions.headers = headers;
  
          return this.http.get('http://localhost:8081/' + '/account/login',
              httpOptions)
              .map(resp =&gt; {
                  // login successful if there's a jwt token in the response
                  const user = resp.json().principal; // the returned user object is a principal object
                  if (user) {
                      // store user details  in local storage to keep user logged in between page refreshes
                      localStorage.setItem('currentUser', JSON.stringify(user));
                  }
              });
      }
  
  
      logOut() {
          // remove user from local storage to log user out
          return this.http.post('http://localhost:8081/' + 'logout', {})
              .map(resp =&gt; {
                  localStorage.removeItem('currentUser');
              });
  
      }
  }
  </code></pre>
  <p>error : deprecated symbol used
  please help me changing the code in Angular 5 (<code>RequestOptions</code>)</p>