[BUG] PUT/PATCH on File SubmodelElement deletes Attachment file

[aaronzi]

Describe the bug
When Updating a file SubmodelElement (without changing the value of the file SME), the attachment file get's deleted. This is due to how updating the element works. First the Element get's deleted and then replaced by the new element coming from the users request. Deleting the element includes the deletion of the attachment.

To Reproduce
Steps to reproduce the behavior:

1. Go to a file SME including an attachment
2. Update the file SME via PUT request (e.g. the desciption)
3. try to fetch the attachment again of that file SME
4. See a 404 error

Expected behavior
When the path does not get updated or the file deleted entirely, the attachment should not get removed.

BaSyx (please complete the following information):

• BaSyx Version: 2.0.0-SNAPSHOT
• BaSyx SDK: Java V2
• AAS Version: DotAAS V3