[web] fix headers on 304 responses (closes #11466875) The response MUST include the following header fields: [...] - ETag and/or Content-Location, if the header would have been sent in a 200 response to the same request https://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.3.5 Unfortunately we weren't copying headers from what would have been the 200 response, but from the request.

from yams.buildobjs import ComputedRelation, EntityType, RelationDefinition
from cubicweb.schema import RRQLExpression

class Subject(EntityType):
    pass

class Object(EntityType):
    pass

class relation(RelationDefinition):
    subject = 'Subject'
    object = 'Object'

class computed(ComputedRelation):
    rule = 'S relation O'
    __permissions__ = {'read': (RRQLExpression('S is ET'),)}