security: add FAQ for domain verification (#21888)

## Description
- Kapa had an [uncertain
response](https://app.kapa.ai/6e2e867c-43a5-47b9-8f1f-9f092b5d81b3/conversations/4f6c5bd9-6814-4e77-9b29-6b9109ab5845)
when a user asked about verifying a domain for multiple orgs
- Added FAQ to add as a Kapa source for improved answer

## Related issues or tickets
https://docker.atlassian.net/browse/ENGDOCS-2384

## Reviews
- [ ] Editorial review

Author: sarahsanders-docker

content/manuals/security/faqs/single-sign-on/domain-faqs.md

@@ -23,3 +23,7 @@ Adding and verifying a domain is required to enable and enforce SSO. See [Config
 ### Is IdP-initiated authentication supported?
 
 IdP-initiated authentication isn't supported by Docker SSO. Users must initiate sign-in through Docker Desktop or Hub.
+
+### Can I verify the same domain on multiple organizations?
+
+You can't verify the same domain for multiple orgnaizations at the organization level. If you want to verify one domain for multiple organizations, you must have a Docker Business subscription, and [create a company](/manuals/admin/company/new-company.md). A company enables centralized management of organizations and allows domain verification at the company level.