Added BackOfficeHost property in Security Settings article

[eshanrnh]

📋 Description

The BackOfficeHost property is missing in the Security Settings article.

Currently, I have only added it to the v16 file. Once it's good to go, I'll add it to the other versions as well.

📎 Related Issues (if applicable)

Fixes #7550

✅ Contributor Checklist

I've followed the Umbraco Documentation Style Guide and can confirm that:

• Code blocks are correctly formatted.
• Sentences are short and clear (preferably under 25 words).
• Passive voice and first-person language (“we”, “I”) are avoided.
• Relevant pages are linked.
• All links work and point to the correct resources.
• Screenshots or diagrams are included if useful.
• Any code examples or instructions have been tested.
• Typos, broken links, and broken images are fixed.

Product & Version (if relevant)

CMS v13, 15, 16, 17

Deadline (if relevant)

Anytime

📚 Helpful Resources

• 🧾 Umbraco Contribution Guidelines
• ✍️ Umbraco Documentation Style Guide

[iOvergaard]

Nice, very descriptive!

Note that the option was first introduced in V14 :-)