docs(controller): document authentication providers (Local, LDAP, OIDC)

[sanderson]

Summary

• Add task-based pages for local, LDAP, and OIDC authentication; broaden the authorization reference to cover identity providers; and update the settings and configuration-options reference to include the new authentication knobs.
• Add new Telegraf Enterprise upgrade shortcode that includes an upgrade call-to-action.
• Clean up em-dashes (---) in the Telegraf Controller docs.

Checklist

• Rebased/mergeable
• Local build passes (npx hugo --quiet)

[github-actions]

Vale Style Check Results

Metric	Count
Errors	0
Warnings	43
Suggestions	70

Warnings (43)

File	Line	Rule	Message
DOCS-SHORTCODES.md	61	write-good.Passive	'is required' may be passive voice. Use active voice if you can.
DOCS-SHORTCODES.md	168	write-good.Passive	'is changed' may be passive voice. Use active voice if you can.
DOCS-SHORTCODES.md	173	write-good.Passive	'are limited' may be passive voice. Use active voice if you can.
DOCS-SHORTCODES.md	173	write-good.Passive	'be closed' may be passive voice. Use active voice if you can.
DOCS-SHORTCODES.md	175	write-good.TooWordy	'indicate' is too wordy.
DOCS-SHORTCODES.md	175	write-good.Passive	'be processed' may be passive voice. Use active voice if you can.
DOCS-SHORTCODES.md	180	write-good.Passive	'is used' may be passive voice. Use active voice if you can.
DOCS-SHORTCODES.md	180	write-good.Passive	'be closed' may be passive voice. Use active voice if you can.
DOCS-SHORTCODES.md	182	write-good.TooWordy	'indicate' is too wordy.
DOCS-SHORTCODES.md	182	write-good.Passive	'be processed' may be passive voice. Use active voice if you can.
DOCS-SHORTCODES.md	187	write-good.Passive	'are forced' may be passive voice. Use active voice if you can.
DOCS-SHORTCODES.md	192	write-good.Passive	'be wrapped' may be passive voice. Use active voice if you can.
DOCS-SHORTCODES.md	192	write-good.Passive	'be closed' may be passive voice. Use active voice if you can.
DOCS-SHORTCODES.md	194	write-good.TooWordy	'indicate' is too wordy.
DOCS-SHORTCODES.md	194	write-good.Passive	'be processed' may be passive voice. Use active voice if you can.
DOCS-SHORTCODES.md	269	write-good.Passive	'be read' may be passive voice. Use active voice if you can.
DOCS-SHORTCODES.md	295	write-good.Passive	'is added' may be passive voice. Use active voice if you can.
DOCS-SHORTCODES.md	301	write-good.Passive	'be used' may be passive voice. Use active voice if you can.
DOCS-SHORTCODES.md	395	write-good.Passive	'being tested' may be passive voice. Use active voice if you can.
DOCS-SHORTCODES.md	516	write-good.TooWordy	'In many cases' is too wordy.

Showing first 20 of 43 warnings.

---

✅ Check passed

[github-actions]

PR Preview Action v1.4.8
🚀 Deployed preview to https://influxdata.github.io/docs-v2/pr-preview/pr-7277/
on branch gh-pages at 2026-05-29 22:22 UTC

[jstirnaman]

Just a couple of nits. Nice!