[improve][admin] Not allow to terminate system topic.

[Technoboy-]

Fixes #15891

Master Issue: #15891

Motivation

Pulsar-manager could see all the topics including the system topic and can terminate them. If terminates system topic by mistake, there would cause many serious problems. So it's better not allow to terminate the system topic.

Documentation

• doc-not-needed
  (Please explain why)

[github-actions]

@Technoboy- Please provide a correct documentation label for your PR.
Instructions see Pulsar Documentation Label Guide.

[mattisonchao]

What about terminating the partitioned topic?

[Technoboy-]

What about terminating the partitioned topic?

Not allowed. The logic is here

pulsar/pulsar-broker/src/main/java/org/apache/pulsar/broker/admin/impl/PersistentTopicsBase.java

Lines 3686 to 3691 in e1c0ad3

	.thenAccept(partitionMetadata -> {
	if (partitionMetadata.partitions > 0) {
	throw new RestException(Status.METHOD_NOT_ALLOWED,
	"Termination of a partitioned topic is not allowed");
	}
	})