Implement custom exceptions

[obrunsmann]

Unity SDK throws an ApiResponseException in case there is any issue with the API response including StatusCode and Message. I guess it
would be nice to also group all API Exceptions into one SDK owned class which can be handeled by the user:

• HTTP socket exception
• Request timeout
• Abnormal status code
• Runtime errors

[GenildoNogueira]

Hello, I've been waiting for this for a while now.
I'm doing it this way!

[ERROR:flutter/runtime/dart_vm_initializer.cc(40)] Unhandled Exception: gRPC Error (code: 6, codeName: ALREADY_EXISTS, message: Username is already in use., details: [], rawResponse: null, trailers: {})

class AuthRepositoryRemote extends AuthRepository {
final _log = Logger('AuthRepositoryRemote');

final NakamaService _nakamaService;

AuthRepositoryRemote({
required NakamaService nakamaService,
}) : _nakamaService = nakamaService;

@OverRide
Future<Result<void, Failure>> register({
required String username,
required String email,
required String password,
}) async {
try {
_currentSession = await _nakamaService.client.authenticateEmail(
email: email,
username: username,
password: password,
create: true,
);

  return Success(null);
} on Exception catch (e) {
  final error = parseGrpcError(e.toString());
  _log.warning(error['message']);
  return Error(RegisterException(customMessage: error['message']));
} finally {
  notifyListeners();
}

}
}

Map<String, dynamic> parseGrpcError(String error) {
final regex = RegExp(
r'gRPC Error (code: (?\d+), codeName: (?[\w_]+), message: (?.?), details: (?

[.?]), rawResponse: (?.?), trailers: (?{.?}))',
);
final match = regex.firstMatch(error);

if (match != null) {
return {
'code': int.tryParse(match.namedGroup('code')!),
'codeName': match.namedGroup('codeName'),
'message': match.namedGroup('message'),
'details': jsonDecode(match.namedGroup('details')!),
'rawResponse': match.namedGroup('rawResponse') == 'null'
? null
: match.namedGroup('rawResponse'),
'trailers': jsonDecode(match.namedGroup('trailers')!),
};
} else {
throw FormatException('Erro gRPC não está no formato esperado.');
}
}

flutter: [AuthRepositoryRemote] Username is already in use.