Apply ordering to querysets in paginated endpoints

[seanpreston]

Bug Description

Some of our paginated endpoints don't use a consistent ordering on the query sets they paginate. This means that the ordering can change between queries, and as such can lead to pagination where the same record is repeated on multiple pages. As per the Postgres spec (https://www.postgresql.org/docs/current/queries-order.html) if no sorting is explicitly chosen, rows will be returned in an unspecified order.

Affected Endpoints

1. /connection
2. /dataset
3. /policy
4. /storage/config

Expected Behaviour

• Objects should be returned ordered by their .created_at field in descending order. ie. most recent objects first.