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'

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summary: Cache presence from remote users
...

Introduction
============

This module stores a timestamp of the latest presence received from
users contacts so that the client can see who is online faster when they
sign in, and won't have to wait for remote servers to reply.

Configuration
=============

Just enable the module.

    modules_enabled = {
        -- more modules
        "presence_cache";
    }

Advanced configuration
======================

The size of the cache is tuneable:

    presence_cache_size = 99

Compatibility
=============

Requires 0.10 or later