prosody: Switch to and enable mod_lastlog2

This records a timestamp of various account events - account registration
time, last connection and last disconnection.

In the future I would like to keep a time-limited record of account activity
so we can also present it to the user for security purposes (e.g. detecting
account compromise and access by third-parties). That will need additional
design work to figure out how to do it in a privacy-preserving way.

ansible/files/prosody.cfg.lua

@@ -86,6 +86,7 @@ modules_enabled = {
 		"snikket_client_id";
 		"snikket_ios_preserve_push";
 		"snikket_restricted_users";
+		"lastlog2";
 
 	-- Spam/abuse management
 		"spam_reporting"; -- Allow users to report spam/abuse

ansible/tasks/prosody.yml

@@ -87,7 +87,7 @@
     - mod_compact_resource
     - mod_conversejs
     - mod_migrate_http_upload
-    - mod_lastlog
+    - mod_lastlog2
     - mod_limit_auth
     - mod_password_policy
     - mod_roster_allinall