Angular ts (front-end) + spring boot (back-end) OAuth2 flow - spring-boot

Question

I want to implement authorization via Google and Microsoft in my full stack app (Angular 6 for front-end, Spring boot for back-end) and I've got a problem.
I follow this scheme which describes how the flow should be implemented:
OAuth2 Authorization Flow:
The problem is with Step 4 where front-end should send authorization code to back-end. I just don't know which endpoint to use and how to configure it in Spring Security configuration.
This endpoint should get authorization code, check it on OAuth provider side, request access and refresh token and remember the authorized user.
Maybe there is an example of how it should be done? Google answers do not seem appropriate.
What I already did:
Added #EnableOAuth2Sso annotation to the security configuration. But this is not what I actually need, because it enables authorization on back-end side. (redirecting to Google page works from back-end, but I need from front-end)
#EnableOAuth2Sso
public class SecurityConfiguration extends WebSecurityConfigurerAdapter {
...
}
Tried configuring Oauth2Login by myself.
#Override
protected void configure(HttpSecurity http) throws Exception {
http
.authorizeRequests().anyRequest().authenticated()
.and()
.oauth2Login()
.clientRegistrationRepository(clientRegistrationRepository)
.authorizedClientService(new InMemoryOAuth2AuthorizedClientService(clientRegistrationRepository));
}
Gradle dependencies:
<pre>
compile 'org.springframework.security.oauth.boot:spring-security-oauth2-autoconfigure:2.0.0.RELEASE'
compile 'org.springframework.security:spring-security-oauth2-jose'
compile 'org.springframework.security:spring-security-oauth2-client'
</pre>
What I expect:
Some endpoint on back-end side, which accepts authorization code. For example:
URL: localhost:8080/oauth2/authcode/google
<pre>
{
"authorization_code": "...."
}
</pre>
And returns access token:
<pre>
{
"access_token": "...",
"expires": "..."
}
</pre>
And what is happening in the middle: back-end exchanges authorization code to access token and refresh token and saves it to own DB.
Thank you!