TP: represent tenants as a hierarchical visualization rather than a flat list

[mitchell852]

I'm submitting a ...

• improvement request (usability, performance, tech debt, etc.)

Traffic Control components affected ...

• Traffic Portal

Current behavior:

In TP, the list of tenants (https://tp.domain.tld/#!/tenants) is represented as a flat list of tenants when tenancy is hierarchical.

New behavior:

The tenants UI should represent the hierarchy visually.

Minimal reproduction of the problem with instructions:

Navigate to https://tp.domain.tld/#!/tenants and notice that the hierarchical tenancy tree is visualized as a flat list making it hard to see the parent/child relationships between the tenants.

Anything else:

Since the data structure is hierarchical, the visualization should be as well. I.e. a tree representation that can be expanded/collapsed.

Also, it would be nice if the user can view delivery services that are:
a. directly assigned to a tenant or
b. accessible to the tenant via the tenant hierarchy