Coding test notes

A sample data can be found in the example directory.

Thing to discuss

This current implementation is based around speed and memory efficiency, as so we whoose to work as close to the metal as possible and Serde has been put aside as it would have occured a performance penalty that we judge unnecessary (see Parsing csv with Serde and zero allocation for more details about performance).
Should a frozen client's account state occuring after a Chargeback affect all other transaction type, or a Deposit is allowed ?
We chose not to use any async because the order of the transations matters. In a server/clients case this would need refactoring.
We chose to add a check to discard any Withdrawal if there is not enough available amount in a client's account. It might need some thought as an ATM in some cases does allow it.
We use the type system to ensure the correctness when parsing.
For performance reason we used an unsafe parsing method of numerical values, but it's fine because we are protected by the type system and infinity check are in place.