AccountNotFoundException to be thrown when not found account with id

ApiError to use in return body of exceptions

RestExceptionHandler to handler exceptions in general

TransactionRuleException to be thrown when rule exception happened

EntityLockWrapper to help handler concurrency thread

TransactionRequestVo to use for request transfer

TransactionController endpoint to handler transfer

TransactionRequestVoBuilder to help object creation in tests

TransactionControllerTest to test transfer endpoint

TransactionResourceConcurrentTest to test concurrency thread

junit-platform.properties to enabled parallel tests

Inserted @RequiredArgsConstructor lombok annotation in a AccountsController class in order to have less code

Inserted @RequiredArgsConstructor lombok annotation in a AccountsService class in order to have less code

Changed getAccount in a AccountsService to handler not found account

Changed Account class to implement EntityLockWrapper.Lockable to handler concurrency thread and added new attribute called ReentrantLock

Created new method called executeTransfer in a AccountsRepository class

Created new method called executeTransfer in a AccountsRepositoryInMemory class, to implements interface

Created new method called transfer in AccountsService to handler transfer

Created new method called sendNotification in AccountsService to call notifyAboutTransfer method

Created new method called isValueNegative in AccountsService to validate negative value

Created new method called isBalanceNotSufficient in AccountsService to validate not sufficient value

Created new method called unlockAccount in AccountsService to handler concurrency thread

Changed AccountsServiceTest to add new transfer tests

1 - Change it to use real database

2 - Create new entity called Client to associate it to Account

3 - Create endpoints to handler Client entity, maybe another microservice