Can you write me a client$-$server architecture for a paying system which : $1.$ should be accessible through web browser, mobile client for IOS and Android. $2.$ the system have two types of users$-$regular which have limited access to the functions and premium users which have access to all system functions. $3.$ A user can register through email, username and password or with external systems like Google and Facebook. A user can log in through email or username and password or with external system. $4.$ Every user has a budget which is a set of their own expenses. There are two types of budgets $-$ individual which is only for one user and shared which is created from one user and shared with up to $4$ other users. $5.$ Every user can create a budget or be part of another shared budget. $6.$ A new expense to the budget can be added through a photo of the receipt, an online paying system like paypal, revolut and etc. or though filing a form. $7.$ Regular users can access the functionality reports with which they can see all of their budgets and expenses. A regular user can become premium if they subscribe to a monthly payment to the system. $8.$ A premium user have access to Analyses section. This section provides the user with analyses for their budgets. $9.$With this system the user can pay with Revolut, Paypal, Skrill or debit card.