Unsupported Want-Digest headers

[acoburn]

The test suite expects a 4xx failure response for requests containing an unsupported Want-Digest header.

For example, given Want-Digest: abc in the request, the test suite expects a 400 Bad Request response.

This, however, does not align with RFC 3230. Nowhere does it state in that specification that a server, when presented with an unsupported digest value, must (or even should) respond with a 4xx error. In fact, there is already a simple mechanism defined by RFC 3230 to determine whether a digest is supported: look for it in the Digest header of the response.

If a client sends an unsupported Want-Digest value, such as abc, the test suite should simply verify that no Digest: abc=<....> value is present in the response.