Implement server state handling in ChatController and ChatService, add ServerStateMapper utility, and create/update server state unit tests.

backend/src/main/java/com/alttd/altitudeweb/controllers/chat/ChatController.java

@@ -28,7 +28,7 @@ public class ChatController implements ChatApi {
 
     @Override
     public ResponseEntity<Void> updateServerStates(ServerStateDto serverStateDto) {
-        //TODO [Stijn] [2026-07-18]: Implement handling server state updates (push to listeners)
-        throw new UnsupportedOperationException("Not implemented");
+        chatService.updateServerState(serverStateDto);
+        return new ResponseEntity<>(HttpStatus.ACCEPTED);
     }
 }

backend/src/main/java/com/alttd/altitudeweb/controllers/chat/ServerStateMapper.java

@@ -0,0 +1,24 @@
+package com.alttd.altitudeweb.controllers.chat;
+
+import com.alttd.altitudeweb.model.ServerStateDto;
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
+import lombok.experimental.UtilityClass;
+
+@UtilityClass
+public class ServerStateMapper {
+    private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper()
+            .registerModule(new JavaTimeModule())
+            .enable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
+            .disable(SerializationFeature.WRITE_DATE_TIMESTAMPS_AS_NANOSECONDS);
+
+    public static String toJson(ServerStateDto serverStateDto) {
+        try {
+            return OBJECT_MAPPER.writeValueAsString(serverStateDto);
+        } catch (JsonProcessingException e) {
+            throw new IllegalStateException("Failed to serialize ServerStateDto to JSON", e);
+        }
+    }
+}

backend/src/main/java/com/alttd/altitudeweb/services/chat/ChatService.java

@@ -2,11 +2,14 @@ package com.alttd.altitudeweb.services.chat;
 
 import com.alttd.altitudeweb.controllers.chat.ChatMessage;
 import com.alttd.altitudeweb.controllers.chat.ChatMessageMapper;
+import com.alttd.altitudeweb.controllers.chat.ServerStateMapper;
 import com.alttd.altitudeweb.database.Databases;
 import com.alttd.altitudeweb.database.chat.ChatLogMapper;
 import com.alttd.altitudeweb.database.web_db.chat_session.ChatSession;
 import com.alttd.altitudeweb.database.web_db.chat_session.ChatSessionMapper;
 import com.alttd.altitudeweb.model.PermissionClaimDto;
+import com.alttd.altitudeweb.model.ServerDto;
+import com.alttd.altitudeweb.model.ServerStateDto;
 import com.alttd.altitudeweb.services.chat.event_publisher.EventPublisher;
 import com.alttd.altitudeweb.services.chat.event_publisher.EventUser;
 import com.alttd.altitudeweb.services.chat.event_publisher.MessageForUser;
@@ -121,6 +124,20 @@ public class ChatService {
         sendMessagesToListeners(chatMessageList);
     }
 
+    public void updateServerState(ServerStateDto serverStateDto) {
+        sendToUsers("server-state", (eventUser) -> {
+            if (eventUser.hasPermission(PermissionClaimDto.HEAD_MOD)) {
+                return ServerStateMapper.toJson(serverStateDto);
+            }
+
+            List<ServerDto> filteredServers = serverStateDto.getServers().stream()
+                    .filter(serverDto -> Arrays.asList(allowedServers).contains(serverDto.getName()))
+                    .toList();
+
+            return ServerStateMapper.toJson(new ServerStateDto().servers(filteredServers));
+        });
+    }
+
     private void sendMessagesToListeners(List<ChatMessage> chatMessageList) {
         Map<ChatMessage, String> jsonCache = new HashMap<>();
         for (ChatMessage message : chatMessageList) {