mod_rest: Workaround lack of number coercion in util.datamapper for HTTP upload util.datamapper will not coerce a string into an integer like the XEP-0363 'size' slot, which becomes a problem when using the HTTP GET method, passing fields as ?query parameters which are always strings.

This module lets you block connections to remote servers at the s2s
level.

``` {.lua}
modules_enabled = {
    -- other modules --
    "s2s_blacklist",

}
s2s_blacklist = {
    "proxy.eu.jabber.org",
}
```