fix: add topic existing validation

[proost]

Please add a meaningful description for your change here
fix: #18027

adding validation to check topic exist or not for PubsubIO

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[github-actions]

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[ahmedabu98]

This looks great! can you add a comment on CHANGES.md calling out this new addition?

[proost]

@ahmedabu98
I update "CHANGES.md".

can you review again? because i notice that Write doesn't validate topic. when topic is given statically, check topic is valid or not.

[ahmedabu98]

Thanks! left some comments

[github-actions]

Reminder, please take a look at this pr: @m-trieu @ahmedabu98

[ahmedabu98]

Looks great! thanks for adding this

Will merge when that last workflow passes

[Abacn]

This is breaking Java presubmit:

testPubsubSinkOverride (org.apache.beam.runners.dataflow.DataflowRunnerTest) failed

java.lang.RuntimeException: com.google.api.client.googleapis.json.GoogleJsonResponseException: 403 Forbidden
GET https://pubsub.googleapis.com/v1/projects/project/topics/topic
{
  "code": 403,
  "errors": [
    {
      "domain": "global",
      "message": "Method doesn't allow unregistered callers (callers without established identity). Please use API Key or other form of API consumer identity to call this API.",
      "reason": "forbidden"
    }
  ],
  "message": "Method doesn't allow unregistered callers (callers without established identity). Please use API Key or other form of API consumer identity to call this API.",
  "status": "PERMISSION_DENIED"
}
	at org.apache.beam.sdk.io.gcp.pubsub.PubsubIO$Write.validate(PubsubIO.java:1658)

#18027 was a very old Issue. Is it still needed here?

[Abacn]

This is a breaking change. Pipeline construction environment may not have access to the PubSub. Here it should either be fail safe or not enabled by default.

[proost]

@Abacn
Oh, I missed that point. How about disabled as default? Checking topic existence is needed.

[Abacn]

How about disabled as default?

sounds good

[Abacn]

Well, I am going to revert the change for now, as introducing a required field in IO connector specification would generally breaks upgrade compatibility of pipelines (unless tested not to be the case).