mod_roster_command: Fix subscription when the "user JID" is a bare domain. Do not attempt to update the roster when the user is bare domain (e.g. a component), since they don't have rosters and the attempt results in an error: $ prosodyctl mod_roster_command subscribe proxy.example.com contact@example.com xxxxxxxxxxFailed to execute command: Error: /usr/lib/prosody/core/rostermanager.lua:104: attempt to concatenate local 'username' (a nil value) stack traceback: /usr/lib/prosody/core/rostermanager.lua:104: in function 'load_roster' /usr/lib/prosody/core/rostermanager.lua:305: in function 'set_contact_pending_out' mod_roster_command.lua:44: in function 'subscribe'

# About

This module allows using the [mod_csi_simple][doc:modules:mod_csi_simple]
setting `csi_important_payloads` (added in trunk/0.12) in Prosody 0.11.x.

# Config

```
modules_enabled = {
    -- other modules etc
    "csi_simple",
    "csi_simple_compat",
}

csi_important_payloads = {
    -- Anything in this namespace:
    "{urn:example:important-namespace}",
    -- Specific element name and namespace:
    "{urn:example:xmpp:priority}super-important",
}
```

# Example

``` lua
csi_important_payloads = {
    -- XEP-0353: Jingle Message Initiation
    "{urn:xmpp:jingle-message:0}",
}
```