OZG-4097 receive-attachment: Persist attachments before mapping

...n/postfach/osiv2/attachment/Osi2AttachmentFileMapper.java

.../postfach/osiv2/attachment/Osi2AttachmentFileService.java

...stfach/osiv2/attachment/Osi2PersistAttachmentService.java

...loud/nachrichten/postfach/osiv2/model/AttachmentInfo.java

...cloud/nachrichten/postfach/osiv2/model/FileChunkInfo.java

...loud/nachrichten/postfach/osiv2/model/Osi2Attachment.java

...zgcloud/nachrichten/postfach/osiv2/model/Osi2Message.java

...achrichten/postfach/osiv2/transfer/Osi2MessageMapper.java

...hrichten/postfach/osiv2/transfer/Osi2PostfachService.java

...ichten/postfach/osiv2/transfer/Osi2QuarantineService.java

...achrichten/postfach/osiv2/transfer/Osi2RequestMapper.java

...chrichten/postfach/osiv2/transfer/Osi2ResponseMapper.java

...ten/postfach/osiv2/transfer/PostfachApiFacadeService.java

...ichten/postfach/osiv2/OsiPostfachRemoteServiceITCase.java

...hrichten/postfach/osiv2/OsiPostfachRemoteServiceTest.java

...en/postfach/osiv2/exception/Osi2ExceptionHandlerTest.java

...postfach/osiv2/extension/AttachmentExampleUploadUtil.java

...iv2/factory/MessageExchangeReceiveMessageTestFactory.java

...actory/MessageExchangeSendMessageResponseTestFactory.java

...ten/postfach/osiv2/factory/Osi2FileUploadTestFactory.java