Add some Example for complex data

[sehHeiden]

Description

Could you please add some description on https://pywps.readthedocs.io/projects/PyWPS-Demo/en/latest/flask.html how to deal with complex input and output as in buffer for example.
I tried to do the buffering from some local files. But that did not work.

I always get: No applicable error code, please check error log. And the Error log, dies not show a reason: Request rejected due to exception.

The link I tried was: http://127.0.0.1:5000/wps?service=WPS&request=Execute&version=1.0.0&identifier=buffer&DataInputs=poly_in=@xlink:href=.gml@method=POST@encoding=UTF-8@schema=.xsd;buffer=10&ResponseDocument=buff_out

Environment

• operating system: Ubuntu 20.04
• Python version: 3.10.6
• PyWPS version: 3.5.2 from pypi
• PyWPS-flask from git