Fix /admin/purge routes returning 404

[kartikynwa]

Endpoints like /admin/purge/person were returning a 404. Nesting /purge as a service inside the /admin service fixes the problem. I am guessing actix-web descends into the /admin block since it is placed first then returns 404 when it does not find a /purge route within it.

Calling the endpoint after these changes:

 ❯ ./purge_user.sh
+ data='{  "person_id": 3,  "auth": "authtoken",  "reason": "terrible poster"}'
+ curl -i -H 'Content-Type: application/json' -X POST -d '{  "person_id": 3,  "auth": "authtoken",  "reason": "terrible poster"}' http://localhost:8536/api/v3/admin/purge/person
HTTP/1.1 200 OK
content-length: 16
access-control-expose-headers: content-type
access-control-allow-credentials: true
vary: Origin, Access-Control-Request-Method, Access-Control-Request-Headers
content-type: application/json
date: Wed, 21 Jun 2023 14:16:19 GMT

{"success":true}%

[dessalines]

LGTM. We should probably add some tests for purge in our jest api_tests/ at some point.