- Takes OrgReg url and api key as arguments
- Assumes that the OrgReg api has been registered behind a Gravitee
  instance.
- Introduces active and deleted fields to OrganizationalUnit for
  keeping track of status in OrgReg. Logic should be introduced in the
  future to ensure that Sponsors and Guests are not connected to
  deleted or inactive OUs.
- Add search and orgreg_id to Admin interface of OUs.

Type checking is now also done for management commands and the usual
missing imports errors are ignored.

Fixes: GREG-13

Fixes: GREG-13

Apparently django_filters is missing type hints.

Fixes: GREG-13

We should be developing against Python 3.9.

Fixes: GREG-13