Filter Hosts by `is_oa_host`

Needed to find the oA hosts if you have a lot of hosts (over 100).

For example we have a multi oA node setup and want to find the oA host among all other hosts added to oA, we need to filter the hosts that have a running oA on them with the backend.

Via the API, we get by default 20 entries of host with one query. We can set the page size to a max size of 100 to get 100 hosts with one call. But if you have more hosts in the system we would have to iterate over the pages to filter in the frontend for all oA nodes.