If you want to create the server in a location, you must set location to the ID or name as listed in /locations. This is the recommended way. You can be even more specific by setting datacenter to the ID or name as listed in /datacenters. However directly specifying the datacenter is discouraged since supply availability in datacenters varies greatly and datacenters may be out of stock for extended periods of time or not serve certain server types at all.
Improved version of #12
See https://docs.hetzner.cloud/#resources-servers-post: