[Issue 1105][pulsaradmin] fix AutoTopicCreation for type non-partitioned

[tomjo]

Fixes #1105

Motivation

To allow setting the AutoTopicCreation policy to non-partitioned it is required to not send the partitions parameter, by making Partitions a pointer instead of an int this is possible.

Modifications

Change type of Partitions in TopicAutoCreationConfig from int to *int

Verifying this change

• Make sure that the change passes the CI checks.

I tested it by using it in our application as the admin code currently does not have much test code. I saw here #1085 that there are reorganization plans + setting up test scaffolding in the future.

[tisonkun]

@tomjo can you elaborate a bit for the use case where this change makes difference?

[tomjo]

We're using a component that publishes messages to a topic with a generated name, so we want to use topic auto creation for the namespace so that these topics are automatically created. We don't need partitions for these topics so we want the default for topic auto creation to be non-partitioned. This is not possible now (see linked issue) since the Partitions int field in the struct has a default value of 0 causing it to be added to the request body of the api call, which pulsar rejects with an error. By making it a pointer, it can be nil and it is not serialized in the body allowing the api call to succeed in setting the auto topic creation policy to enabled and non-partitioned.

We're currently using topic auto creation with type partitioned and 1 partition which works but it would be nicer if the client supports what the rest api supports