Updates room size API to work with multiple domains.

Checks for a parameter named subdomain and if it exists, adds it to the roomname as used in multiple domain mode ([subdomain]roomname@conference.example.com).
Moves muc_size module to per-host module and adds token verification.

resources/prosody-plugins/mod_muc_size.lua

 -- Prosody IM
 -- Copyright (C) 2017 Atlassian
 --
---
 -- This module requires net-url module
 -- Install it using #luarocks install net-url
 
-module:set_global(); -- Global module
-
-local split_jid = require "util.jid".split;
-local st = require "util.stanza";
+local jid = require "util.jid";
 local it = require "util.iterators";
 local json = require "util.json";
 local iterators = require "util.iterators";
 local neturl = require "net.url";
 local parse = neturl.parseQuery;
 
-function get_room_from_jid(jid)
-	local node, host = split_jid(jid);
+-- option to enable/disable room API token verifications
+local enableTokenVerification
+    = module:get_option_boolean("enable_roomsize_token_verification", false);
+
+local token_util = module:require "token/util".new(module);
+
+-- no token configuration but required
+if token_util == nil and enableTokenVerification then
+    log("error", "no token configuration but it is required");
+    return;
+end
+
+-- required parameter for custom muc component prefix,
+-- defaults to "conference"
+local muc_domain_prefix
+    = module:get_option_string("muc_mapper_domain_prefix", "conference");
+
+--- Finds and returns room by its jid
+-- @param room_jid the room jid to search in the muc component
+-- @return returns room if found or nil
+function get_room_from_jid(room_jid)
+	local _, host = jid.split(room_jid);
 	local component = hosts[host];
 	if component then
 		local muc = component.modules.muc
 		if muc and rawget(muc,"rooms") then
 			-- We're running 0.9.x or 0.10 (old MUC API)
-			return muc.rooms[jid];
+			return muc.rooms[room_jid];
 		elseif muc and rawget(muc,"get_room_from_jid") then
 			-- We're running >0.10 (new MUC API)
-			return muc.get_room_from_jid(jid);
+			return muc.get_room_from_jid(room_jid);
 		else
 			return
 		end
 	end
 end
 
+--- Verifies room name, domain name with the values in the token
+-- @param token the token we received
+-- @param room_address the full room address jid
+-- @return true if values are ok or false otherwise
+function verify_token(token, room_address)
+    if not enableTokenVerification then
+        return true;
+    end
+
+    -- if enableTokenVerification is enabled and we do not have token
+    -- stop here, cause the main virtual host can have guest access enabled
+    -- (allowEmptyToken = true) and we will allow access to rooms info without
+    -- a token
+    if token == nil then
+        log("warn", "no token provided");
+        return false;
+    end
+
+    local session = {};
+    session.auth_token = token;
+    local verified, reason = token_util:process_and_verify_token(session);
+    if not verified then
+        log("warn", "not a valid token %s", tostring(reason));
+        return false;
+    end
+
+    if not token_util:verify_room(session, room_address) then
+        log("warn", "Token %s not allowed to join: %s",
+            tostring(token), tostring(room_address));
+        return false;
+    end
+
+    return true;
+end
+
+--- Handles request for retrieving the room size
+-- @param event the http event, holds the request query
+-- @return GET response, containing a json with participants count,
+--         tha value is without counting the focus.
 function handle_get_room_size(event)
 	local params = parse(event.request.url.query);
 	local room_name = params["room"];
 	local domain_name = params["domain"];
-	local room_address = room_name .. "@" .. "conference." .. domain_name;
+    local subdomain = params["subdomain"];
+
+    local room_address
+        = jid.join(room_name, muc_domain_prefix.."."..domain_name);
+
+    if subdomain and subdomain ~= "" then
+        room_address = "["..subdomain.."]"..room_address;
+    end
+
+    if not verify_token(params["token"], room_address) then
+        return 403;
+    end
+
 	local room = get_room_from_jid(room_address);
 	local participant_count = 0;
 
 		if occupants then
 			participant_count = iterators.count(room:each_occupant());
 		end
-		log("debug", "there are %s occupants in room", tostring(participant_count));
+		log("debug",
+            "there are %s occupants in room", tostring(participant_count));
 	else
 		log("debug", "no such room exists");
 	end
 	return GET_response;
 end
 
+--- Handles request for retrieving the room participants details
+-- @param event the http event, holds the request query
+-- @return GET response, containing a json with participants details
 function handle_get_room (event)
 	local params = parse(event.request.url.query);
 	local room_name = params["room"];
 	local domain_name = params["domain"];
-	local room_address = room_name .. "@" .. "conference." .. domain_name;
+    local subdomain = params["subdomain"];
+    local room_address
+        = jid.join(room_name, muc_domain_prefix.."."..domain_name);
+
+    if subdomain ~= "" then
+        room_address = "["..subdomain.."]"..room_address;
+    end
+
+    if not verify_token(params["token"], room_address) then
+        return 403;
+    end
+
 	local room = get_room_from_jid(room_address);
 	local participant_count = 0;
 	local occupants_json = array();
 			    end
 			end
 		end
-		log("debug", "there are %s occupants in room", tostring(participant_count));
+		log("debug",
+            "there are %s occupants in room", tostring(participant_count));
 	else
 		log("debug", "no such room exists");
 	end
 	return GET_response;
 end;
 
-function module.add_host(module)
-	module:depends("http");
+function module.load()
+    module:depends("http");
 	module:provides("http", {
 		default_path = "/";
 		route = {