[doc][improvement] enable geo-replication at topic level need extra config

[youzipi]

Motivation

i try to enable the topic level geo-replication in my cluster,
when i execute ./pulsar-admin topics set-replication-clusters public/default/repl-test --clusters standalone,aliyun-test, i got error:

2022-07-19T09:05:09,444+0000 [AsyncHttpClient-7-1] WARN  org.apache.pulsar.client.admin.internal.BaseResource - [http://localhost:8080/admin/v2/persistent/public/default/repl-test/replication] Failed to perform http post request: javax.ws.rs.NotAllowedException: HTTP 405 Topic level policies is disabled, to enable the topic level policy and retry.
Topic level policies is disabled, to enable the topic level policy and retry.

Reason: Topic level policies is disabled, to enable the topic level policy and retry.

after enable the topic error, try again, i got a 500 error:

2022-07-21T03:37:17,796+0000 [AsyncHttpClient-7-1] WARN  org.apache.pulsar.client.admin.internal.BaseResource - [http://localhost:8080/admin/v2/persistent/public/default/repl-test/replication] Failed to perform http post request: javax.ws.rs.InternalServerErrorException: HTTP 500 Topic policies service is disabled.

 --- An unexpected error occurred in the server ---

Message: Topic policies service is disabled.

Stacktrace:

java.lang.UnsupportedOperationException: Topic policies service is disabled.
	at org.apache.pulsar.broker.service.TopicPoliciesService$TopicPoliciesServiceDisabled.updateTopicPoliciesAsync(TopicPoliciesService.java:151)
	at org.apache.pulsar.broker.admin.impl.PersistentTopicsBase.lambda$internalSetReplicationClusters$215(PersistentTopicsBase.java:3119)
	at java.base/java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:1072)
	at java.base/java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:506)
	at java.base/java.util.concurrent.CompletableFuture.complete(CompletableFuture.java:2073)
	at org.apache.pulsar.client.util.RetryUtil.lambda$executeWithRetry$2(RetryUtil.java:62)
	at java.base/java.util.concurrent.CompletableFuture.uniWhenComplete(CompletableFuture.java:859)
	at java.base/java.util.concurrent.CompletableFuture.uniWhenCompleteStage(CompletableFuture.java:883)
	at java.base/java.util.concurrent.CompletableFuture.whenComplete(CompletableFuture.java:2251)
	at org.apache.pulsar.client.util.RetryUtil.executeWithRetry(RetryUtil.java:48)
	at org.apache.pulsar.client.util.RetryUtil.lambda$retryAsynchronously$0(RetryUtil.java:42)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:304)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
	at java.base/java.lang.Thread.run(Thread.java:829)

after search the doc, i could not found any information about the Topic policies service.
then i found these in code:

// org.apache.pulsar.broker.PulsarService#start
            // Start topic level policies service
            if (config.isTopicLevelPoliciesEnabled() && config.isSystemTopicEnabled()) {
                this.topicPoliciesService = new SystemTopicBasedTopicPoliciesService(this);
            }
//     default value:
private TopicPoliciesService topicPoliciesService = TopicPoliciesService.DISABLED;

means i need to configure the systemTopicEnabled too,
the error msg is somewhat confuse.

i also think that we need more information about the topic policy service

Modifications

add necessary tips

Documentation

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[youzipi]

@Anonymitaet

[Anonymitaet]

Thanks for your contribution!

1. Before submitting a doc PR, please preview your changes locally. When submitting a PR, please attach the screenshots of your local preview. In this way, you can get your PR reviewed and merged more quickly.

2. Does this change apply to multiple doc versions? If so, please update them all.

Thank you! 😊

[youzipi]

this tip should be displayed in all 2.10.x versions doc at least.
as:

• this configuration is enabled by default after 2.11.0.
• topic level geo-replication is introduced in 2.10.0.

@Anonymitaet