This commit adds a new ACL rule named "peering" to authorize
actions taken against peering-related endpoints.
The "peering" rule has several key properties:
- It is scoped to a partition, and MUST be defined in the default
namespace.
- Its access level must be "read', "write", or "deny".
- Granting an access level will apply to all peerings. This ACL rule
cannot be used to selective grant access to some peerings but not
others.
- If the peering rule is not specified, we fall back to the "operator"
rule and then the default ACL rule.