SDK: Subscriber hat keinen Zugriff auf die AttachemntID
### Description of the bug:
In der Klasse Attachment fehlt die AttachmentID.
Hintergrund: In der fachlichen Nachricht referenziert ein Kunde die Attachments, wobei der Filename oft nicht eindeutig ist. Theoretisch kann die AttachmentID in der Klasse Metadata gesetzt werden.Im SDK hat man bei senderClient.send(sendableSubmission) keinen Zugriff auf dieses Objekt. Auch der Umweg über senderClient.send(final SendableEncryptedSubmission sendableEncryptedSubmission) ist ungeeignet, da dort zwar die AttachmentID gesetzt werden kann, aber nur im Kontext versenden (verschlüsseln, signieren usw.).
### Current behavior:
Ein Subscriber hat mit dem SDK keinen Zugriff auf die AttachmentID
### Expected behavior:
Die wesentlichen Eigenschaften eines Attachments, wie filename, purpose, attachmentId, description und mimeType sind über das SDK auch für einen Subscriber erreichbar.
```
"attachments": [
{
"filename": "meinBild.jpg",
"purpose": "attachment",
"attachmentId": "82150376-b506-4d25-7ead-eb69b74e2f10",
"description": "Passbild (F99000582)",
"mimeType": "image/jpeg",
"hash": {
"type": "sha512",
"content": "49487...f2f72"
}
}
]
```
### Environments:
ALLE
### Additional Information:
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### Dependency / relationship to other issues:
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### Responsible person / team:
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### Contact persons including contact details:
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### Screenshots / Logs / Requests:
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### Checklist:
- [ ] Add Severity label
- [ ] Add team label
- [ ] Related/affected issues/stories/epics linked and explained in the bug issue
- [ ] Creation of an automated test
- [ ] Bugfix deployed on DEV
- [ ] Bugfix tested on DEV
- [ ] Bugfix deployed on TEST
- [ ] Bugfix tested on TEST (possibly also by the connection project itself)
- [ ] Successful fix reported to Team Operations (Teams channel)
- [ ] Bugfix deployed on STAGE
- [ ] Bugfix tested on STAGE if necessary
- [ ] Bugfix deployed on PROD
- [ ] Bugfix tested on PROD (possibly also by the connection project itself)
- [ ] Final communication by Team Operations if necessary
- [ ] Internal documentation was checked and updated if necessary
- [ ] External documentation has been checked and updated if necessary
- [ ] Updated changelog if necessary
### Approach/Solution:
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### Release version of the artifact:
issue