creating user gives incorrect status code

## Describe the bug
According to https://owncloud.dev/libre-graph-api/#/educationUser/CreateEducationUser creating user should give `201`

## Steps to reproduce
1. create an education user

## Expected behavior
the status code should be `201`
https://owncloud.dev/libre-graph-api/#/educationUser/CreateEducationUser

## Actual behavior
the status code is `200`

## Setup
Please describe how you started the server and provide a list of relevant environment variables or configuration files.

```console
OCIS_IMAGE=owncloud/ocis-rolling:latest
```

## Additional context
Add any other context about the problem here.