With the completion of
FCREPO-2688, an ACL can be assigned to a resource based on resource creation (via a PUT or a POST). The spec indicates that a 400 or 500 series message should returned if the resource does not exist. If the acl specified in the link does not exist a 400 is returned without a clear explanation in a rel="http://www.w3.org/ns/ldp#constrainedBy" link. See https://fcrepo.github.io/fcrepo-specification/#link-acl-on-create
There are two tasks to be completed with this jira:
1. in the case that the acl URI in the link header does not exist, return a 409 with a constrainedBy link that indicates the non existence of the URI.
2. if the acl URI exists but does not contain a triple indicating rdf:type of http://fedora.info/definitions/v4/webac#Acl (ie <> a webac:Acl ) return a 409 with a constrainedBy that indicates the fact that the resource is not correctly typed.