Spring OAuth2 with saving user and subsequent work with the API through the token

Question

I really need help with spring security. I studied the documentation in detail, but I could not understand many things. Some sample code is missing. I just don't know where to start.

Necessary:

• authorize the user via OAuth2,
• save the user to the database, since there are relationships in the tables to the User entity (I can’t imagine how you can do without saving).
• save the token or substitute it in headers. Needed in order to work with the resource server API through a user token.

In general, I plan to use VK as a resource server. But I know that there will also be difficulties. To begin with, I would like to do this for Google or Github.

I will be glad for any help! Code examples in which the items above are configured, I would also be grateful!

I sort of figured out the simplest authorization and wrote the following code:

@Configuration
@EnableWebFluxSecurity
public class OAuth2LoginSecurityConfig {

    @Bean
    public SecurityWebFilterChain securityWebFilterChain(ServerHttpSecurity http) {
        http
            .authorizeExchange(authorize -> authorize
                .anyExchange().authenticated()
            )
            .oauth2Login(withDefaults());

        return http.build();
    }
}

I can't move further. Perhaps I understand something wrong.