added 404 status in contract

kafka-ui-api/src/test/java/com/provectus/kafka/ui/KafkaConsumerTests.java

@@ -65,4 +65,15 @@ public class KafkaConsumerTests extends AbstractBaseTest {
                 .expectBodyList(TopicMessage.class)
                 .hasSize(0);
     }
+
+    @Test
+    public void shouldReturn404ForNonExistingTopic() {
+        var topicName = UUID.randomUUID().toString();
+
+        webTestClient.delete()
+                .uri("/api/clusters/{clusterName}/topics/{topicName}/messages", LOCAL, topicName)
+                .exchange()
+                .expectStatus()
+                .isNotFound();
+    }
 }

kafka-ui-contract/src/main/resources/swagger/kafka-ui-api.yaml

@@ -328,6 +328,8 @@ paths:
       responses:
         200:
           description: OK
+        404:
+          description: Not found
 
   /api/clusters/{clusterName}/consumer-groups/{id}:
     get: