Eagerly fetch csrf token for single page application

src/main/java/de/webalf/slotbot/configuration/authentication/website/AuthenticationSuccessHandler.java

@@ -0,0 +1,27 @@
+package de.webalf.slotbot.configuration.authentication.website;
+
+import jakarta.servlet.ServletException;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import org.springframework.security.core.Authentication;
+import org.springframework.security.web.authentication.SavedRequestAwareAuthenticationSuccessHandler;
+import org.springframework.security.web.csrf.CsrfToken;
+import org.springframework.stereotype.Component;
+
+import java.io.IOException;
+
+/**
+ * @author Alf
+ * @since 21.02.2023
+ */
+@Component
+public class AuthenticationSuccessHandler extends SavedRequestAwareAuthenticationSuccessHandler {
+	@Override
+	public void onAuthenticationSuccess(HttpServletRequest request, HttpServletResponse response, Authentication authentication) throws ServletException, IOException {
+		// https://github.com/spring-projects/spring-security/issues/12094#issuecomment-1294150717
+		CsrfToken csrfToken = (CsrfToken) request.getAttribute(CsrfToken.class.getName());
+		csrfToken.getToken();
+
+		super.onAuthenticationSuccess(request, response, authentication);
+	}
+}

src/main/java/de/webalf/slotbot/configuration/authentication/website/OAuth2EndpointConfig.java

@@ -37,6 +37,7 @@
 @RequiredArgsConstructor(onConstructor_ = @Autowired)
 public class OAuth2EndpointConfig {
 	private final DiscordAuthenticationService discordAuthenticationService;
+	private final AuthenticationSuccessHandler authenticationSuccessHandler;
 
 	@Bean
 	protected SecurityFilterChain oAuthUserFilterChain(HttpSecurity http) throws Exception {
@@ -65,6 +66,7 @@ protected SecurityFilterChain oAuthUserFilterChain(HttpSecurity http) throws Exc
 				.oauth2Login()
 				.loginPage("/oauth2/authorization/discord")
 				.defaultSuccessUrl("/events")
+				.successHandler(authenticationSuccessHandler)
 				.tokenEndpoint().accessTokenResponseClient(accessTokenResponseClient())
 				.and()
 				.userInfoEndpoint().userService(oAuthUserService());