refactor: add data as attachment to replies, use byte[] for data internally (planning#2251)

...main/java/dev/fitko/fitconnect/api/FitConnectService.java

...va/dev/fitko/fitconnect/api/config/ApplicationConfig.java

...in/model/metadata/attachment/AttachmentForValidation.java

...itko/fitconnect/api/domain/sender/SendableSubmission.java

...connect/api/domain/sender/steps/unencrypted/DataStep.java

...fitko/fitconnect/api/domain/subscriber/SendableReply.java

...fitconnect/api/domain/subscriber/steps/ReplyDataStep.java

...fitconnect/api/services/validation/ValidationService.java

...ava/dev/fitko/fitconnect/client/sender/ReplyReceiver.java

.../dev/fitko/fitconnect/client/sender/SubmissionSender.java

...a/dev/fitko/fitconnect/client/subscriber/ReplySender.java

...itko/fitconnect/client/subscriber/SubmissionReceiver.java

.../dev/fitko/fitconnect/client/util/DataAttachmentUtil.java

...ev/fitko/fitconnect/client/util/DestinationValidator.java

...a/dev/fitko/fitconnect/core/FitConnectDefaultService.java

.../fitconnect/core/validation/DefaultValidationService.java

...st/java/dev/fitko/fitconnect/client/SenderClientTest.java

...itko/fitconnect/client/util/DestinationValidatorTest.java

...v/fitko/fitconnect/core/FitConnectDefaultServiceTest.java

...connect/core/validation/DefaultValidationServiceTest.java