Description of change

Instead of loading the account from storage and saving on each operation, we'll keep the account references stored on the AccountManager struct, wrapped on Arc<RwLock<>> for thread safety. This prevents race conditions between e.g. the polling system and the transfer API, where account data can be lost.

Type of change

• Refactor

How the change has been tested

Unit tests + faucet.

Change checklist

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have checked that new and existing unit tests pass locally with my changes