* Do not raise unretryable exceptions in ResolveRemoteAccountService
* Removed fatal exceptions from ResolveRemoteAccountService
Exceptions that cannot be retried should not be raised. New exception
class for those that can be retried (Mastodon::UnexpectedResponseError)
* Refactor ResolveRemoteAccountService
* Remove trailing whitespace
* Use redis locks around critical ResolveRemoteAccountService code
* Add test for race condition of lock
Eugen Rochko