Support service role (backport #1445)

[mergify]

This adds support for the service role that is
used in the Secure RBAC community goal in OpenStack.

This is matched against what API calls that Ceilometer
and Aodh does against the Gnocchi API.

---

This is an automatic backport of pull request #1445 done by Mergify.

[mergify]

Cherry-pick of dc96190 has failed:

On branch mergify/bp/stable/4.6/pr-1445
Your branch is up to date with 'origin/stable/4.6'.

You are currently cherry-picking commit dc96190.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	new file:   releasenotes/notes/service-role-ffc61f0a1d1de20d.yaml

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   gnocchi/rest/policies.py

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[mergify]

This pull request has been removed from the queue for the following reason: checks failed.

The merge conditions cannot be satisfied due to failing checks:

• 🛑 check (build)

You may have to fix your CI before adding the pull request to the queue again.

If you want to requeue this pull request, you can post a @mergifyio requeue comment.