Group names are returned in lowercase in the response of REST requests

Steps to reproduce:

1. Create a group and give it the name "FOO" (uppercase)
2. Make a GET request to this endpoint `/rest/api/group/FOO`

What happens:

In the response of the REST API the group name is always lowercase. Also, for example, if that group is added to the permissions of some space and then the permissions are queried through a REST request then the group name is also lowercase in the response.

What should happen:

The REST endpoints should return the group names in the correct case.