feat: add async queries

[r-o-b-o-t-o]

Adds async queries for the world, characters and auth databases (WorldDBQueryAsync, CharDBQueryAsync, AuthDBQueryAsync)

local PLAYER_EVENT_ON_COMMAND = 42

local function SyncQueryExample()
	-- Hangs the server for 5 seconds while the query executes because of the SLEEP(5)
	query = CharDBQuery("SELECT guid, account, name, level, SLEEP(5) FROM characters LIMIT 3")
	if not query then
		return
	end

	repeat
		local guid, account, name, level = query:GetUInt32(0), query:GetUInt32(1), query:GetString(2), query:GetUInt8(3)
		print("GUID: " .. tostring(guid) .. ", account: " .. tostring(account) .. ", name: " .. name .. ", level: " .. tostring(level))
	until not query:NextRow()
end

local function AsyncQueryExample()
	-- Doesn't hang the server even with SLEEP(5) because we're using CharDBQueryAsync
	CharDBQueryAsync("SELECT guid, account, name, level, SLEEP(5) FROM characters LIMIT 3", function(query)
		if not query then
			return
		end

		repeat
			local guid, account, name, level = query:GetUInt32(0), query:GetUInt32(1), query:GetString(2), query:GetUInt8(3)
			print("GUID: " .. tostring(guid) .. ", account: " .. tostring(account) .. ", name: " .. name .. ", level: " .. tostring(level))
		until not query:NextRow()
	end)
end

RegisterPlayerEvent(PLAYER_EVENT_ON_COMMAND, function(event, player, command, chathandler)
	if command == "sync" then
		print("Executing sync query...")
		SyncQueryExample()
		return false
	elseif command == "async" then
		print("Executing async query...")
		AsyncQueryExample()
		return false
	end

	return true
end)