Tenant: implement update and delete operations

[nqb]

Is your feature request related to a problem? Please describe.
At the moment, you can create tenant using pfcmd tenant add and get a list of tenants in web admin. However, it's not possible to update settings related to tenant (portal_domain_name and domain_name) using pfcmd or GUI. Also I don't see any possibility to delete a tenant.

Describe the solution you'd like

• Implement update and delete operations on backend
• Manage tenants from web admin (Create, Read, Update and Delete)

[julsemaan]

We need a proper GUI for the tenants and be able to CRUD them like we do with Nodes and Users

This section should only be available to the master tenant (global)

@jrouzierinverse would be better placed to expose the API to CRUD the tenants (if it doesn't exist already)

[jrouzierinverse]

The API is already there.

[jrouzierinverse]

I would need to restrict it to the Global Tenant.

[satkunas]

@jrouzierinverse are all API endpoints exposed? Should I proceed with ui?