Our suggestion is to not go down this path. Multi-tenancy was very popular back in the time when people used to deploy one single application on a huge application server. In the era of cloud computing, it's much easier to have different deployments, per tenant, and dimensioned according to their individual needs. Of course that adds pressure on the operation side as you will need to manage and monitor each one of them.
Ultimately, having separated deployments is a better solution because you can easily remove it and delete all tenants data without affecting the others. Also, if you have a tenant heavily using the system, you can scale up their installation accordingly and their usage won't affect the other tenants. Additionally, you can even have different billing plans according to their needs and usage.
That said, if you really want to have them cohabiting the same Lagom deployment, you will need to partition the data using the tenant id. You will need to take that in account on every single place in your application. This will also add complexity to your application, and is why we suggest the above approach instead.