Add OpenAPI Authentication and Authorization details for the API

[DL6ER]

What does this implement/fix?

See title, no functional change.

Related issue or feature (if applicable): N/A

Pull request in docs with documentation (if applicable): This is the documentation change.

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2. I have commented my proposed changes within the code.
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4. It is compatible with the EUPL 1.2 license
5. I have squashed any insignificant commits. (git rebase)

Checklist:

• The code change is tested and works locally.
• I based my code and PRs against the repositories developmental branch.
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[DL6ER]

https://ftl.pi-hole.net/openAPI/security/docs/#delete-/auth

No auth needed ✅

Auth needed ✅