fix: import or update autolinks on creation

[acouvreur]

Resolves #2565

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Before the change?

Creating a github_repository_autolink_reference resource whose key_prefix already existed in the repository failed immediately with a 422 Unprocessable Entity error from the GitHub API. There was no way to adopt an existing autolink into Terraform state through a normal apply; the only workaround was a manual terraform import.

After the change?

The Create function now looks up existing autolinks by key_prefix before calling the GitHub API:

• Same settings (target_url_template and is_alphanumeric match): the existing autolink is silently imported into state, making the operation idempotent.
• Different settings: the existing autolink is deleted first, then a new one is created with the desired configuration, providing an in-place update on first apply.
• No existing autolink: behaviour is unchanged; the autolink is created normally.

Pull request checklist

• Schema migrations have been created if needed (example)
• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• Yes
• No

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AI Disclaimer: This was developed with the help of Claude Sonnet 4.6

[github-actions]

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