test: add unit test that deletes abandoned workspace (#7990)

* test: add unit test that deletes abandoned workspace

This is to ensure we do not break this functionality in future.
This is important incase this edge case happens, an admin can
clean up the abandoned resources.

coderd/database/dbfake/dbfake.go

@@ -4646,11 +4646,19 @@ func (q *fakeQuerier) UpdateUserDeletedByID(_ context.Context, params database.U
 			u.Deleted = params.Deleted
 			q.users[i] = u
 			// NOTE: In the real world, this is done by a trigger.
-			for i, k := range q.apiKeys {
+			i := 0
+			for {
+				if i >= len(q.apiKeys) {
+					break
+				}
+				k := q.apiKeys[i]
 				if k.UserID == u.ID {
 					q.apiKeys[i] = q.apiKeys[len(q.apiKeys)-1]
 					q.apiKeys = q.apiKeys[:len(q.apiKeys)-1]
+					// We removed an element, so decrement
+					i--
 				}
+				i++
 			}
 			return nil
 		}