fix(kafka): Make producer proxy equality reflexive

Return true when the Kafka producer proxy is compared with itself. This preserves existing delegate equality behavior for other comparisons while satisfying the equals contract.

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

Author: adinauer

sentry-kafka/src/main/java/io/sentry/kafka/SentryKafkaProducer.java

@@ -126,6 +126,13 @@ static final class SentryProducerHandler<K, V> implements InvocationHandler {
         }
       }
 
+      if ("equals".equals(method.getName())
+          && args != null
+          && args.length == 1
+          && proxy == args[0]) {
+        return true;
+      }
+
       if ("toString".equals(method.getName()) && (args == null || args.length == 0)) {
         return "SentryKafkaProducer[delegate=" + delegate + "]";
       }

sentry-kafka/src/test/kotlin/io/sentry/kafka/SentryKafkaProducerTest.kt

@@ -347,6 +347,20 @@ class SentryKafkaProducerTest {
     assertNotNull(record.headers().lastHeader(SentryKafkaProducer.SENTRY_ENQUEUED_TIME_HEADER))
   }
 
+  @Test
+  fun `wrapped producer equals itself`() {
+    val producer = SentryKafkaProducer.wrap(delegate, scopes)
+
+    assertTrue(producer.equals(producer))
+  }
+
+  @Test
+  fun `wrapped producer keeps delegate hashCode`() {
+    val producer = SentryKafkaProducer.wrap(delegate, scopes)
+
+    assertEquals(delegate.hashCode(), producer.hashCode())
+  }
+
   @Test
   fun `toString includes delegate`() {
     val producer = SentryKafkaProducer.wrap(delegate, scopes)