Ready solution for game currency?

Question

Mobile development

For the service (web + mobile applications), it became necessary to add virtual points for users (similar to game currency, VK votes, and so on) with the ability to credit them, transfer them to another user (or receive them), spend them inside the system, and so on.
Are there ready-made solutions (SaaS service or Open Source) that could be integrated so as not to be implemented independently?