Creation date is missing for space members

## Describe the bug
Space members are currently missing the `createdDateTime` property in the server response.

## Steps to reproduce
1. Create a project space
2. Add a member to this space
3. Request its members via `/graph/v1beta1/drives/{driveId}/root/permissions`

## Expected behavior
The members/permissions have a `createdDateTime` property.

## Actual behavior
The `createdDateTime` property is missing.

Note that the same goes for responses of `POST` and `PATCH` requests for creating/updating members.