Implementation-specific behaviors

[acoburn]

The test suite makes use of some implementation-specific interactions, that are not defined in the Fedora specification nor any of the associated specifications. In particular, the use of a http://fedora.info/definitions/v4/repository#ServerManaged prefer header as well as another prefer header with a value of handling=lenient; received=minimal. The handling=lenient part is defined in RFC 7240, but I've never seen any specification define received=minimal