Validate autolink prefix

[Jwels1]

Resolves #3176

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Before the change?

• Before there was no validation that the key_prefix had to not end in a number but from issue [BUG]: autolink allows numbers during plan, but fails during apply #3176 if it did then you'd receive this error on apply but not on plan:

422 Validation Failed [{Resource:KeyLink Field:key_prefix Code:custom Message:key_prefix must not end with a number} {Resource:KeyLink Field:key_prefix Code:custom Message:key_prefix must only contain letters, numbers, or .-_+=:/#}]

After the change?

• Terraform plan will throw an error during plan due to a failure to validate key_prefix

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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[github-actions]

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[deiga]

Thanks for the contribution! It's a nice Quality of Life improvement ☺️

Left a minor comment

[Jwels1]

@deiga good catch, you're right that it does work just the same. I applied the suggestion.

[Jwels1]

@deiga or @MarkVaughn Do you guys. have someone else that can approve the PR?