Prepare clients for localized lobby notices

The server change introduces optional notice localization metadata while preserving legacy text. This updates the shared lobby contract first so downstream clients can adopt the fields without raw JSON handling.

Constraint: FAF server PR 1083 adds optional notice localization fields while keeping legacy text for existing clients.
Rejected: Client-only parsing workaround | shared lobby API should model the server contract first.
Confidence: high
Scope-risk: narrow
Directive: Keep the two-argument NoticeInfo constructor available for Java callers until client consumers migrate.
Tested: JAVA_HOME=/Users/yoseph/Codexperiment/.deps/jdk21/Contents/Home ./gradlew :lobby:test --tests com.faforever.commons.lobby.ServerMessageTest
Tested: git diff --check
Not-tested: Full Gradle suite.
Co-authored-by: OmX <omx@oh-my-codex.dev>

Author: 2 people

lobby/src/main/kotlin/com/faforever/commons/lobby/ConnectionApi.kt

@@ -6,6 +6,7 @@ import com.fasterxml.jackson.annotation.JsonProperty
 import com.fasterxml.jackson.annotation.JsonValue
 import reactor.core.publisher.Flux
 import reactor.core.publisher.Mono
+import java.time.OffsetDateTime
 
 /**
  * API to manage connection to the Lobby server
@@ -49,9 +50,15 @@ internal class InvalidResponse : ServerMessage
  * A general message from the server (automated or broadcast from admin) to display to the user.
  * FIXME: Should maybe offer event codes for translations in case of automated responses.
  */
-data class NoticeInfo(
+data class NoticeInfo @JvmOverloads constructor(
   val style: String?,
   val text: String?,
+  @JsonProperty("i18n_key")
+  val i18nKey: String? = null,
+  @JsonProperty("i18n_args")
+  val i18nArgs: List<String> = emptyList(),
+  @JsonProperty("expires_at")
+  val expiresAt: OffsetDateTime? = null,
 ) : ServerMessage
 
 /**
@@ -210,4 +217,3 @@ internal class ClientPingMessage : ClientMessage
  * Holds no data, just checks if the connection is still alive
  */
 internal class ClientPongMessage : ClientMessage
-

lobby/src/test/kotlin/com/faforever/commons/lobby/ServerMessageTest.kt

@@ -101,6 +101,33 @@ class ServerMessageTest {
     assertEquals(NoticeInfo("kill", "boo"), result)
   }
 
+  @Test
+  fun deserializeLocalizableNoticeInfo() {
+    val result = objectMapper.readValue<ServerMessage>(
+      """
+      {
+        "command": "notice",
+        "style": "error",
+        "text": "You are banned from FAF until 2026-05-10T22:00:00+00:00. Reason: test",
+        "i18n_key": "login.error.banned",
+        "i18n_args": ["2026-05-10T22:00:00+00:00", "test"],
+        "expires_at": "2026-05-10T22:00:00+00:00"
+      }
+    """.trimIndent()
+    )
+
+    assertEquals(
+      NoticeInfo(
+        "error",
+        "You are banned from FAF until 2026-05-10T22:00:00+00:00. Reason: test",
+        "login.error.banned",
+        listOf("2026-05-10T22:00:00+00:00", "test"),
+        OffsetDateTime.parse("2026-05-10T22:00:00+00:00")
+      ),
+      result
+    )
+  }
+
   @Test
   fun deserializeGameJoinFailed() {
     val result = objectMapper.readValue<ServerMessage>(