GAIAXAUTH-13: setup integration with keycloak

Closes GAIAXAUTH-13

app/src/main/java/eu/gaiax/difs/aas/config/SecurityConfig.java

+package eu.gaiax.difs.aas.config;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.security.config.Customizer;
+import org.springframework.security.config.annotation.web.builders.HttpSecurity;
+import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
+import org.springframework.security.web.SecurityFilterChain;
+
+@EnableWebSecurity
+public class SecurityConfig {
+
+    @Bean
+    SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
+        http
+          .authorizeRequests(authorizeRequests ->
+            authorizeRequests.anyRequest().authenticated()
+          )
+          .oauth2Login(oauth2Login ->
+            oauth2Login.loginPage("/oauth2/authorization/aas-app"))
+          .oauth2Client(Customizer.withDefaults());
+        return http.build();
+    }
+    
+}
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