mod_account_activity: Record an account's last activity timestamp

This is similar to mod_lastlog/mod_lastlog2.

Some functionality was dropped, compared to mod_lastlog2. These features
(recording the IP address, or tracking the timestamp of multiple events) are
handled better by the mod_audit family of modules. For example, those
correctly handle multiple logins, IP address truncation, and data retention
policies.

The "registered" timestamp from mod_lastlog2 was also dropped, as this has
been stored in account_details by Prosody itself since at least 0.12 already.

plugins/mod_account_activity.lua

@@ -0,0 +1,109 @@
+local jid = require "util.jid";
+local time = os.time;
+
+local store = module:open_store(nil, "keyval+");
+
+module:hook("authentication-success", function(event)
+	local session = event.session;
+	if session.username then
+		store:set_key(session.username, "timestamp", time());
+	end
+end);
+
+module:hook("resource-unbind", function(event)
+	local session = event.session;
+	if session.username then
+		store:set_key(session.username, "timestamp", time());
+	end
+end);
+
+local user_sessions = prosody.hosts[module.host].sessions;
+function get_last_active(username) --luacheck: ignore 131/get_last_active
+	if user_sessions[username] then
+		return os.time(), true; -- Currently connected
+	else
+		local last_activity = store:get(username);
+		if not last_activity then return nil; end
+		return last_activity.timestamp;
+	end
+end
+
+module:add_item("shell-command", {
+	section = "user";
+	section_desc = "View user activity data";
+	name = "activity";
+	desc = "View the last recorded user activity for an account";
+	args = { { name = "jid"; type = "string" } };
+	host_selector = "jid";
+	handler = function(self, userjid) --luacheck: ignore 212/self
+		local username = jid.prepped_split(userjid);
+		local last_timestamp, is_online = get_last_active(username);
+		if not last_timestamp then
+			return true, "No activity";
+		end
+
+		return true, ("%s (%s)"):format(os.date("%Y-%m-%d %H:%M:%S", last_timestamp), (is_online and "online" or "offline"));
+	end;
+});
+
+module:add_item("shell-command", {
+	section = "migrate";
+	section_desc = "Perform data migrations";
+	name = "account_activity_lastlog2";
+	desc = "Migrate account activity information from mod_lastlog2";
+	args = { { name = "host"; type = "string" } };
+	host_selector = "host";
+	handler = function(self, host) --luacheck: ignore 212/host
+		local lastlog2 = module:open_store("lastlog2", "keyval+");
+		local n_updated, n_errors, n_skipped = 0, 0, 0;
+
+		local async = require "util.async";
+
+		local p = require "util.promise".new(function (resolve)
+			local async_runner = async.runner(function ()
+				local n = 0;
+				for username in lastlog2:items() do
+					n = n + 1;
+					if n % 100 == 0 then
+						self.session.print(("Processed %d..."):format(n));
+						async.sleep(0);
+					end
+					local lastlog2_data = lastlog2:get(username);
+					if lastlog2_data then
+						local current_data, err = store:get(username);
+						if not current_data then
+							if not err then
+								current_data = {};
+							else
+								n_errors = n_errors + 1;
+							end
+						end
+						if current_data then
+							local imported_timestamp = current_data.timestamp;
+							local latest;
+							for k, v in pairs(lastlog2_data) do
+								if k ~= "registered" and (not latest or v.timestamp > latest) then
+									latest = v.timestamp;
+								end
+							end
+							if latest and (not imported_timestamp or imported_timestamp < latest) then
+								local ok, err = store:set_key(username, "timestamp", latest);
+								if ok then
+									n_updated = n_updated + 1;
+								else
+									self.session.print(("WW: Failed to import %q: %s"):format(username, err));
+									n_errors = n_errors + 1;
+								end
+							else
+								n_skipped = n_skipped + 1;
+							end
+						end
+					end
+				end
+				return resolve(("%d accounts imported, %d errors, %d skipped"):format(n_updated, n_errors, n_skipped));
+			end);
+			async_runner:run(true);
+		end);
+		return p;
+	end;
+});