[FEAT]: Support for multiple wallets

[pohodnya]

Is your feature request related to a problem? Please describe.
The payment system in our product is designed in such a way that customers can have several service contracts at the same time. The movement of funds under each contract is carried out separately and we cannot use the funds received under one contract to write off for services under another contract. Legally, this is only possible with the consent of the user and by making a corrective write-off for each invoice. Also, different contracts may have different taxation systems. All this together makes it impossible to use one wallet. In our business model and within our legal conditions, every subscription should be directly pointed to wallet that it uses for withdraws by invoices.

Describe the solution you'd like
We want to be able to:

1. create multiple wallets for one customer
2. specify Wallet for Customer's Subscription
3. issue Invoice for topping up specified Wallet
4. debit money for transactions and subscriptions only from the wallet that is linked to the subscription

Describe alternatives you've considered

1. Using one wallet. But as I described in the problem, this becomes impossible due to a number of reasons: different taxation systems, the need for user consent when conducting transactions and making adjustment write-offs in the accounting system.
2. Creating several customers for one client. This is just a crutch. In theory, this can work, but in this case we will have to duplicate some of the client data (organization and payment details), and also take out some of the logic for supporting several customer payment accounts from the billing system.

Additional context
Google uses a similar approach in payment accounts. For example, I can pay for a Google Workspace subscription and not pay for Google Drive.

https://getlago.canny.io/feature-requests/p/support-for-multiple-wallets