mod_rest: Restore 'kind' property in JSON-mapped objects The datamapper schema has no 'kind' field, instead handling it as a top-level property of the currently unused <xmpp> element and doing this early dispatch on the top level element name. This puts the field back into the output JSON.

This module lets you block connections to any remote servers not on a
whitelist.

``` {.lua}
s2s_whitelist = {
    "example.org",
}
```