Support dash in the parameter name of the URL

[uynap]

For example, I have a downstream endpoint /aaa?cust-nums=1
Normally, we write Sysl as:

    /aaa:
        GET ?cust-nums=string:
            return ok <: Result

But when run the sysl binary, it throw errors below:

mismatched input 'cust-nums=string' expecting Name

At the moment, "-" is not supported in parameter name. Since I can't change the downstream definition, I was wondering whether there's a workaround in Sysl?