decode uri component before redirect for safe redirect

Decoding URI component before redirecting will allow for redirection with all the get parameters along with the previous url. Currently, if a url with get parameter is redirected to, it results in a 404. 


@version101
@nedbat Can we put this behind a feature flag (defaulting to False if it does not exist) so the debug URL is not enabled in production instances? I.e. in urls.py:
`if settings.FEATURE.get('ENABLE_DEBUG_SHOW_PARAMS', False):`
and on the testcase:
`@override_settings((ENABLE_DEBUG_SHOW_PARAMS=True)`