shibboleth fields with UTF-8 content end up badly encoded via wsgi

[olifre]

We have also hit the issue detailed at:
rdmorganiser/rdmo#77
in a self-developed Django application. I could not find a better approach than the one outlined there, which requires an additional feature in this module (optionally urldecoding the fields).

@jochenklar has implemented this in:
rdmorganiser@e2f6cab

I'm not sure whether the code can be upstreamed, but I believe it would be of general use :-).