List Tenant Groups Handler

curl --request GET \
  --url http://localhost:8000/v1/tenant-groups

{
  "items": [
    {
      "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "tenant_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "name": "<string>",
      "description": "<string>",
      "created_at": "2023-11-07T05:31:56Z",
      "updated_at": "2023-11-07T05:31:56Z",
      "member_count": 123
    }
  ],
  "total": 1,
  "limit": 2,
  "offset": 1
}