Adding explict Function Invoke claim for non-Platform tokens

[mathewc]

Adding a new custom claim for direct http invocations. The auth requirements used by the function invocation middleware will require this claim to be present.

Our existing auth handlers for Keys and JWTs have been updated to add the claim to the principle, since those are the only auth schemes supported by the DefaultFunctionPolicy.

Only need to backport to v3. In v1, ONLY key auth is supported for http function invocations.

Pull request checklist

• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• My changes do not need to be backported to a previous version
  • v3 backport: Adding explict Function Invoke claim for non-Platform tokens #9819
• My changes do not require diagnostic events changes
  • Otherwise: I have added/updated all related diagnostic events and their documentation (Documentation issue linked to PR)
• I have added all required tests (Unit tests, E2E tests)

[fabiocav]

Small comment.

[fabiocav]

Flagging as approved, but it would be good to have the claim value updated so that it is lowercased.