RS: Added more details to create CA-signed certs

[rrelledge]

Note

Low Risk
Primarily documentation and small CSS tweaks; low risk aside from potential confusion if any certificate requirements are misstated.

Overview
Documentation update: Greatly expands create-certificates.md to spell out CA-signed certificate requirements (EKU/key usage, SAN DNS patterns, key size/validity, SHA-1 warning), and adds end-to-end procedures for OpenSSL and Windows AD CS (CSR submission, chain assembly, export/convert to PEM), plus new sections for validation commands, installation steps, and common TLS troubleshooting.

Styling: Updates index.css to apply distinct list-style types for nested ordered lists in .prose (decimal → lower-alpha → lower-roman → decimal) to improve readability of multi-level steps.

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[github-actions]

DOC-6065

[github-actions]

Staging links:
https://redis.io/docs/staging/DOC-6065/operate/rs/security/certificates/create-certificates/

[jit-ci]

🛡️ Jit Security Scan Results

✅ No security findings were detected in this PR

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^{Security scan by Jit}

[andy-stark-redis]

One minor suggestion that might improve the clarity of the lists a bit, but otherwise language and links LGTM.

[andy-stark-redis]

Just a thought, but maybe consider using unordered lists for these sublists? I know the sublists still represent ordered sequences of instructions, but the numbering starts looking complicated for a procedure with many steps and sub-steps, like this one.

An alternative might be to see if you can use lettered lists for sublists like these. I don't think Markdown supports them directly, but you might be able to do it with some CSS.

[rrelledge]

@andy-stark-redis Thank you! I updated the CSS to use lettered sublists. That's how our old docs site worked anyway, so I was happy to try and change it. Does the updated staged preview seem more readable with the lettered sublists?

[andy-stark-redis]

@rrelledge Yeah, that's exactly what I was thinking, thanks. Looks great and everyone will benefit from this going forward :-)