docs(domain): Add Auth Tokens to Domain Model

[manjeet-04]

Description

Adds a domain model topic for auth tokens. The domain model section had a page
for every resource type except auth tokens.

Changes

• New page: content/boundary/v1.0.x/content/docs/domain-model/auth-tokens.mdx
• Nav entry under Domain model, between "Auth methods" and "Credentials"
• Entry in the "Summary of resources" list on domain-model/index.mdx

Please go to the Preview tab and select the appropriate template:

• Boundary
• Consul
• HCP services
• Nomad

Terraform

• HCP Terraform
• Terraform
• Terraform Enterprise

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[github-actions]

Vercel Previews Deployed

Name	Status	Preview	Updated (UTC)
Dev Portal	✅ Ready (Inspect)	Visit Preview	Thu Sep 17 19:42:25 UTC 2026
Unified Docs API	✅ Ready (Inspect)	Visit Preview	Thu Sep 17 19:38:24 UTC 2026

[github-actions]

Broken Link Checker

This PR contains broken links, but won't be blocked. Use this report to improve content quality:

Quick Actions

• Internal links (HashiCorp sites): Please fix these - they impact user experience
• External links: Consider if these are essential or can be updated/removed
• Temporary issues: External sites may recover - check again before merging

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Internal Links

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Summary

Status	Count
🔍 Total	142
✅ Successful	0
⏳ Timeouts	0
🔀 Redirected	0
👻 Excluded	142
❓ Unknown	0
🚫 Errors	0
⛔ Unsupported	0

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