OAuth2 with Angular and reactive Spring Security

I am trying to implement a social login with VK for my Angular app and Spring Webflux back end. At the moment I have an endpoint on back end to serve user info: localhost:8080/people/me. I tried to authenticate user on front end the following way:

ngOnInit(): void {
    this.http.get(USER_INFO_URL)
      .subscribe((resp: Response) => {
        if (resp.status < 300) {
          this.authenticated = true;
          resp.json()
            .then(vkUser => {
              let fields: [string, string] = ['firstName', vkUser.firstName];
              fields['lastName'] = vkUser.lastName;
              this.user = new User(vkUser.id, fields);
            });
        } else {
          window.location.href = AUTH_URL;
        }
      });
  }

However, when my Spring app redirects the client to VK for authentication, VK does not provide any CORS headers, causing the mechanism to fail.

Could someone please recommend a way of using OAuth2 for Angular/Spring pair? I am using a code flow, so I guess first I need to get the code on front end and then send it to the Spring back end, so that it changes it for access token.

At the same time, I feel like my approach may be wrong and the entire auth process should take place at the back end, while front end should only get a cookie, but then I can't figure how to redirect AJAX request from front end to VK login page, handle that on back end and then return to Angular app.

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