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: Presence deduplication module
labels:
- 'Stage-Alpha'
...

This module tries to squash incoming identical presence stanzas to save
some bandwidth at the cost of increased memory use.

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

  Option                         Type     Default
  ------------------------------ -------- ---------
  presence\_dedup\_cache\_size   number   `100`

The only setting controls how many presence stanzas *per session* are
kept in memory for comparing with incoming presenece.

Requires Prosody 0.10 or later.