Null-Safety-Warnungen der IDE behoben: Methodenreferenzen durch Lambdas ersetzt

Bei einer Methodenreferenz wird der Empfänger zum Parameter des
funktionalen Interfaces, dessen @NonNull-Annotation die Eclipse-Analyse
nicht zusichern kann; als Lambda übernimmt der Parameter die Annotation.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backend/src/main/java/de/appcreation/swyxweb/webhook/WebhookService.java

@@ -86,7 +86,7 @@ public class WebhookService {
     @PreDestroy
     void shutdown() {
         heartbeat.shutdownNow();
-        subscribers.forEach(SseEmitter::complete);
+        subscribers.forEach(emitter -> emitter.complete());
         subscribers.clear();
     }
 

backend/src/main/java/de/appcreation/swyxweb/websocket/SwyxTrayMockHandler.java

@@ -359,7 +359,8 @@ public class SwyxTrayMockHandler extends TextWebSocketHandler {
         String needle = wanted.toLowerCase();
         List<MockContact> hits = MOCK_CONTACTS.stream()
                 .filter(contact -> contact.matches(needle))
-                .sorted(Comparator.comparing(MockContact::name).thenComparing(MockContact::number))
+                .sorted(Comparator.comparing((MockContact contact) -> contact.name())
+                        .thenComparing(contact -> contact.number()))
                 .limit(CONTACT_RESULT_LIMIT)
                 .toList();
         log.info("SwyxTray-Mock: {} Adresseintrag/-einträge zu '{}'", hits.size(), wanted);

backend/src/test/java/de/appcreation/swyxweb/AddressEntryTests.java

@@ -58,7 +58,7 @@ class AddressEntryTests {
 				 "type":"addresses"}""");
 
 		assertThat(entries).hasSize(2);
-		assertThat(entries).extracting(AddressEntry::number).containsExactly("7587", "5215");
+		assertThat(entries).extracting(entry -> entry.number()).containsExactly("7587", "5215");
 	}
 
 	/**

backend/src/test/java/de/appcreation/swyxweb/WebhookControllerTests.java

@@ -10,7 +10,6 @@ import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
 
 import de.appcreation.swyxweb.storage.ArchiveService;
-import de.appcreation.swyxweb.webhook.WebhookEvent;
 import de.appcreation.swyxweb.webhook.WebhookService;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Nested;
@@ -112,7 +111,7 @@ class WebhookControllerTests {
 			.andExpect(status().isOk());
 
 		assertThat(service.history())
-			.extracting(WebhookEvent::channel)
+			.extracting(event -> event.channel())
 			.containsExactly("kunden", "kuriere", "jobs");
 
 		// Kunden und Kuriere landen als Adressdaten in der Ablage, der Job als Job.