Improve already-exists handling and add e2e coverage

[freeznet]

Fixes #368

Motivation

Avoid repeated reconcile failures when topics already exist and prevent schema updates from churning on empty schema.

Modifications

Improve already-exists detection and add e2e coverage for pre-existing topics and empty schema version stability.

Verifying this change

This change added tests and can be verified as follows:

• go test ./pkg/admin/... -v -run TestIsAlreadyExist
• cd tests && ginkgo --trace --progress ./operator

Documentation

• no-need-doc (tests and error handling only)

[github-actions]

@freeznet:Thanks for your contribution. For this PR, do we need to update docs?
(The PR template contains info about doc, which helps others know more about the changes. Can you provide doc-related info in this and future PR descriptions? Thanks)

[github-actions]

license-eye has totally checked 455 files.

Valid	Invalid	Ignored	Fixed
363	1	91	0

Click to see the invalid file list

• pkg/admin/errors_test.go

[Copilot]

Pull request overview

This PR improves error handling for already-existing Pulsar resources and adds end-to-end test coverage for pre-existing topics and schema version stability. The changes prevent unnecessary reconcile failures and schema version churn.

Changes:

• Enhanced IsAlreadyExist error detection to handle multiple error formats and HTTP status codes
• Refactored schema application logic to compare versions and avoid unnecessary uploads
• Added comprehensive unit and e2e tests for pre-existing topics and empty schema handling

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
pkg/admin/errors.go	Improved IsAlreadyExist to handle wrapped errors and string matching for "already exist" messages
pkg/admin/errors_test.go	Added comprehensive test coverage for IsAlreadyExist function
pkg/admin/interface.go	Added GetSchemaInfoWithVersion and GetSchemaVersionBySchemaInfo methods to the interface
pkg/admin/impl.go	Implemented new schema version checking methods
pkg/admin/dummy.go	Added stub implementations for testing
pkg/connection/reconcile_topic.go	Refactored applySchema to use version comparison instead of deep equality
pkg/connection/reconcile_topic_test.go	Added unit tests for schema application logic
tests/operator/resources_test.go	Added e2e tests for pre-existing topics and empty schema version stability
.gitignore	Added mise.toml to ignored files

Comments suppressed due to low confidence (1)

pkg/admin/errors_test.go:1

• The copyright header is duplicated at the beginning of the file. Remove the duplicate copyright header (lines 15-27).

// Copyright 2026 StreamNative

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