chore: cors for openapi

Author: kashike

src/main/java/io/papermc/fill/configuration/SecurityConfiguration.java

@@ -21,6 +21,7 @@
 import org.jspecify.annotations.NullMarked;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.http.HttpMethod;
 import org.springframework.security.authentication.AuthenticationManager;
 import org.springframework.security.config.Customizer;
 import org.springframework.security.config.annotation.authentication.configuration.AuthenticationConfiguration;
@@ -37,12 +38,25 @@
 import org.springframework.security.provisioning.InMemoryUserDetailsManager;
 import org.springframework.security.web.SecurityFilterChain;
 import org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter;
+import org.springframework.web.cors.CorsConfiguration;
+import org.springframework.web.cors.CorsConfigurationSource;
+import org.springframework.web.cors.UrlBasedCorsConfigurationSource;
 
 @Configuration
 @EnableWebSecurity
 @EnableMethodSecurity
 @NullMarked
 public class SecurityConfiguration {
+  @Bean
+  public CorsConfigurationSource corsConfigurationSource() {
+    final UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
+    final CorsConfiguration openapi = new CorsConfiguration();
+    openapi.addAllowedMethod(HttpMethod.GET);
+    openapi.addAllowedOrigin("*");
+    source.registerCorsConfiguration("/openapi.yaml", openapi);
+    return source;
+  }
+
   @Bean
   public PasswordEncoder passwordEncoder() {
     return PasswordEncoderFactories.createDelegatingPasswordEncoder();