Auxiliary tenant is optional when peering in the same tenant

[LaurentLesle]

The add-on can be used to connect a vnet and a vhub in different subscriptions / same tenant or different tenant.
This change adds the support for the same tenant when using azure AD service principals.

virtual_hub_subscription_id = "xxxx"
virtual_hub_tenant_id       = "yyyy"
virtual_hub_lz_key          = "connectivity_virtual_hub1"

virtual_network_subscription_id = "uuuuu"
virtual_network_tenant_id       = "vvvv"

virtual_hub_connections = {
  project2_to_hub1 = {
    name = "project2-to-hub1"
    virtual_hub = {
      lz_key = "connectivity_virtual_hub1"
      key    = "hub1"
    }
    vnet = {
      lz_key   = "project2-resources"
      vnet_key = "project2"
    }
  }
}

[arnaudlh]

LGTM