Make DeadLetterPolicy deserializable

[michaeljmarshall]

Describe the bug
The DeadLetterPolicy is not deserializable.

To Reproduce
Run the following test and you'll see the following error:

    @Test
    public void test() throws Exception {
        ConsumerBuilderImpl builder = new ConsumerBuilderImpl(mock(PulsarClientImpl.class), null);
        DeadLetterPolicy policy = DeadLetterPolicy.builder().deadLetterTopic("a").retryLetterTopic("a").initialSubscriptionName("a").maxRedeliverCount(1).build();
        builder.deadLetterPolicy(policy);
        Map<String, Object> config = new HashMap<>();
        builder.loadConf(config);
    }

java.lang.RuntimeException: Failed to load config into existing configuration data

	at org.apache.pulsar.client.impl.conf.ConfigurationDataUtils.loadData(ConfigurationDataUtils.java:70)
	at org.apache.pulsar.client.impl.ConsumerBuilderImpl.loadConf(ConsumerBuilderImpl.java:88)
	at org.apache.pulsar.client.impl.ConsumerBuilderImplTest.test(ConsumerBuilderImplTest.java:66)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:568)
	at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:132)
	at org.testng.internal.TestInvoker.invokeMethod(TestInvoker.java:599)
	at org.testng.internal.TestInvoker.invokeTestMethod(TestInvoker.java:174)
	at org.testng.internal.MethodRunner.runInSequence(MethodRunner.java:46)
	at org.testng.internal.TestInvoker$MethodInvocationAgent.invoke(TestInvoker.java:822)
	at org.testng.internal.TestInvoker.invokeTestMethods(TestInvoker.java:147)
	at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:146)
	at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:128)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
	at org.testng.TestRunner.privateRun(TestRunner.java:764)
	at org.testng.TestRunner.run(TestRunner.java:585)
	at org.testng.SuiteRunner.runTest(SuiteRunner.java:384)
	at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:378)
	at org.testng.SuiteRunner.privateRun(SuiteRunner.java:337)
	at org.testng.SuiteRunner.run(SuiteRunner.java:286)
	at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:53)
	at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:96)
	at org.testng.TestNG.runSuitesSequentially(TestNG.java:1218)
	at org.testng.TestNG.runSuitesLocally(TestNG.java:1140)
	at org.testng.TestNG.runSuites(TestNG.java:1069)
	at org.testng.TestNG.run(TestNG.java:1037)
	at com.intellij.rt.testng.IDEARemoteTestNG.run(IDEARemoteTestNG.java:66)
	at com.intellij.rt.testng.RemoteTestNGStarter.main(RemoteTestNGStarter.java:109)
Caused by: com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `org.apache.pulsar.client.api.DeadLetterPolicy` (no Creators, like default constructor, exist): cannot deserialize from Object value (no delegate- or property-based Creator)
 at [Source: (String)"{"autoUpdatePartitionsIntervalSeconds":60,"deadLetterPolicy":{"maxRedeliverCount":1,"retryLetterTopic":"a","deadLetterTopic":"a","initialSubscriptionName":"a"},"tickDurationMillis":1000,"replicateSubscriptionState":false,"negativeAckRedeliveryDelayMicros":60000000,"expireTimeOfIncompleteChunkedMessageMillis":60000,"maxPendingChuckedMessage":10,"topicNames":[],"priorityLevel":0,"ackReceiptEnabled":false,"acknowledgementsGroupTimeMicros":100000,"receiverQueueSize":1000,"autoUpdatePartitions":true,"[truncated 549 chars]; line: 1, column: 63] (through reference chain: org.apache.pulsar.client.impl.conf.ConsumerConfigurationData["deadLetterPolicy"])
	at com.fasterxml.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:67)
	at com.fasterxml.jackson.databind.DeserializationContext.reportBadDefinition(DeserializationContext.java:1904)
	at com.fasterxml.jackson.databind.DatabindContext.reportBadDefinition(DatabindContext.java:400)
	at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1349)
	at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1415)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:351)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:184)
	at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:129)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:313)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:176)
	at com.fasterxml.jackson.databind.deser.DefaultDeserializationContext.readRootValue(DefaultDeserializationContext.java:322)
	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4674)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3629)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3597)
	at org.apache.pulsar.client.impl.conf.ConfigurationDataUtils.loadData(ConfigurationDataUtils.java:68)
	... 29 more

Expected behavior
A consumer dead letter policy should be configurable via the loadConf method.

Additional context
The above test was run on a recent version of the master branch.

[cbornet]

Can this be cherry-picker to 2.11 ? It is needed in spring-pulsar

[eolivelli]

@cbornet feel free to cherry-pick it, it is better to commit this API changes before cutting the release