Check repository_deployment_branch_policy for 404 in read

[o-sama]

Resolves #1853

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Before the change?

• Deleting this resource outside of TF currently breaks the configuration.

After the change?

• The provider should be able to recognize when this resource no longer exists.

Pull request checklist

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

Neither of the above is required, there's no functionality change outside of checking for a 404 status when reading the resource.

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• Yes
• No

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[kfcampbell]

Is this the desired behavior? Perhaps when deleted outside of GitHub, the provider should reinstate the resource as described in the HCL. Can you talk to me a little more about what prompted this PR and the scenarios you're hoping to avoid?

[o-sama]

That is the intended behaviour, previously the read would just return the error if it isn't a 304 not found and so nothing would happen. The goal here is to remove the resource from state if it's deleted outside of Terraform, which would then recreate on the next apply to match the code.

I did forget to remove the old error checks though which should not be hit anymore so I'll do that in a commit in a few mins.

This issue is behind opening this PR and shows what a 404 looks like currently for this resource.

[kfcampbell]

@o-sama thank you for the context and explanation!