Comment 2 for bug 1818725

Reviewed: https://review.opendev.org/670926
Committed: https://git.openstack.org/cgit/openstack/keystone/commit/?id=52da4d0e129048d1b808bdde07364cde698cf475
Submitter: Zuul
Branch: master

commit 52da4d0e129048d1b808bdde07364cde698cf475
Author: Guang Yee <email address hidden>
Date: Mon Jul 15 16:57:21 2019 -0700

    implement system scope for application credential

    Implement system scopes, namely 'admin', 'reader', and 'member' for
    the application credential API. Thus, making it consistent with other
    system-scoped policy definitions.

    For the application credential API, the follow policies will be enforced:

    - system admin can fetch, list, lookup, and delete user's application
      credentials.
    - system member and reader can only fetch, list, and lookup user's application
      credentials. Deleting a user's application credential other their own is
      strictly prohibitted.
    - domain and project admins can no longer touch user's application credentials
      other their own.
    - domain and project readers cannot touch user's application credentials
      other their own.
    - domain and project members cannot touch user's application credentials
      other their own.
    - create an application credential can only be done by the owner. No one else
      can create an application credential on behalf of another user.

    Test cases are added to guard the above policy changes.

    Change-Id: I26ee11571b6d0f700a5fe3a62ad2e8fc7f5316fe
    Closes-Bug: 1818725
    Closes-Bug: 1750615