An Arcanist workflow downstream requests information on leases visible to the user. The user is only interested in leases for which //they// are the owner, so Arcanist iterates over the results and returns only the ones with a matching `ownerPHID`. It's //so// much cheaper to have the server do this filtering than the client.
The proposed change will be small but necessary for the above feature, and will allow conduit calls to `drydock.lease.search` to specify an `ownerPHIDs` array as a constraint. Per the use case above, the workflow will provide the authorized user's PHID as owner, but this change enables wider features than only this one.