Can't you just consider the tenantId the same as the feedId? Or use some fixed word, like 'global'? Please don't use the slashes, equal symbols and others :)
As for the inventory, currently the tenant is auto-created with the very first call to the rest api. There is no dedicated endpoint to create the tenant. The tenant id is obtained from the accounts component. Probably, this will be changed to get the tenant id from the http header. So all you need to do is to start inserting the data with the correctly set tenant id header.
jk