Update namespace & topic admin methods to return nil if unset

[klevy-toast]

Fixes #1431

Motivation

For the namespace / topic admin methods that return a pointer, explicitly return nil if the method isn't set (API returns empty body)

Modifications

• New method in client.go GetBodyWithContext that returns body & error
• Modify 14 methods across topic & namespace files to use new method, check the body, and return nil if the body is nil
• Update tests and add new test coverage that was missing

Verifying this change

• Make sure that the change passes the CI checks.

This change added tests and can be verified as follows:

• Added missing test coverage for properties that were not previously tested
• Modified existing test to verify property is nil on initial state / after removal

Does this pull request potentially affect one of the following parts:

If yes was chosen, please highlight the changes

• Dependencies (does it add or upgrade a dependency): (yes / no)
• The public API: (yes / no)
• The schema: (yes / no / don't know)
• The default values of configurations: (yes / no)
• The wire protocol: (yes / no)

Documentation

• Does this pull request introduce a new feature? (yes / no)
• Updated the go docs to mention nil return values on all relevant methods

[lhotari]

test failure:

=== RUN   TestGetTopicAutoCreation
    namespace_test.go:159: 
        	Error Trace:	/pulsar/pulsar-client-go/pulsaradmin/pkg/admin/namespace_test.go:159
        	Error:      	Expected value not to be nil.
        	Test:       	TestGetTopicAutoCreation
        	Messages:   	Expected non-nil when topic auto creation is configured
--- FAIL: TestGetTopicAutoCreation (0.01s)

[klevy-toast]

@lhotari Thanks, fixed up the test issues. I needed to change a bit more in the client package that should be reviewed carefully.

[Copilot]

Pull Request Overview

This PR modifies the behavior of topic and namespace policy getter methods to return nil when policies are not configured at the topic/namespace level, rather than returning default/zero values. This is accomplished by introducing a new GetBodyWithContext method and decodeJSONWithBody helper that detect empty HTTP response bodies.

Key Changes

• Added GetBodyWithContext and decodeJSONWithBody functions to REST client for detecting empty response bodies
• Updated policy getter methods to return nil when policies are not configured (empty response)
• Updated tests to expect nil values instead of zero-value structs when policies are removed or not configured

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
pulsaradmin/pkg/rest/client.go	Added GetBodyWithContext method and decodeJSONWithBody helper to detect and return empty response bodies
pulsaradmin/pkg/admin/topic.go	Updated policy getter methods and documentation to return nil when policies are not configured
pulsaradmin/pkg/admin/topic_test.go	Updated tests to expect nil instead of zero values when policies are not configured
pulsaradmin/pkg/admin/namespace.go	Updated namespace policy getter methods and documentation to return nil when policies are not configured
pulsaradmin/pkg/admin/namespace_test.go	Added comprehensive tests for namespace policies expecting nil for unconfigured policies

Comments suppressed due to low confidence (1)

pulsaradmin/pkg/rest/client.go:220

• Line 220 returns nil, err but err is undefined at this point if the else if !decode block was entered but neither the file != nil nor the else branch returned. This will cause a compilation error or return an undefined error. Should return nil, nil instead.

	return nil, err

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[crossoverJie]

LGTM