Use Arg request, response
response~content_type = "text/plain"
-- The field name "user name" arrives percent- or plus-encoded on the
-- wire (user%20name or user+name). Both must resolve to arg("user name")
-- now that the NAME is decoded with the same DeWeb as the value (v11).
Say "spaced=["request~arg("user name")"]"
Say "exists=["request~arg("user name","Exists")"]"
