feat: add Ledger module and Ledger Transaction schema

[mFragaBA]

Motivation

We want a reliable way to register and track all currency flows (for example, you buy a skin, level up a champion, get some rewards, etc.)

Explain why not how.
Closes #563

Summary of changes

• Added Ledger module with functions to do 2 things:
  • register a user getting some currencies
  • register auser spending some currencies
• Removed functions to add/remove currency from users in Currencies module and replaced all calls with ledger calls

The functions in the ledger module respond to 2 use cases:

• add/remove currency as a single transaction
• add/remove currency as part of a greater transaction

How to test it?

This does many small changes in a lot of places so I would say the way to test it would be to do all currency related actions in game:

• collect quest rewards
• win a game (coming out in 1st, 2nd, 3rd place)
• spend gold to buy skins
• spend gold to level up

Checklist

• Tested the changes locally.
• Reviewed the changes on GitHub, line by line.
• This change requires new documentation.
  • Documentation has been added/updated.