Add TenantGroupColumn to display Tenant Group on tables

Works the same as the existing TenantColumn, but displats the Tenant Group of
the Tenant.

Views should prefetch the Tenants Group for this to be efficient in large
tables.

netbox/tenancy/tables/columns.py

@@ -2,6 +2,7 @@ import django_tables2 as tables
 
 __all__ = (
     'TenantColumn',
+    'TenantGroupColumn',
 )
 
 
@@ -24,3 +25,28 @@ class TenantColumn(tables.TemplateColumn):
 
     def value(self, value):
         return str(value) if value else None
+
+
+class TenantGroupColumn(tables.TemplateColumn):
+    """
+    Include the tenant group description.
+    """
+    template_code = """
+    {% if record.tenant and record.tenant.group %}
+        <a href="{{ record.tenant.group.get_absolute_url }}" title="{{ record.tenant.group.description }}">{{ record.tenant.group }}</a>
+    {% elif record.vrf.tenant and record.vrf.tenant.group %}
+        <a href="{{ record.vrf.tenant.group.get_absolute_url }}" title="{{ record.vrf.tenant.group.description }}">{{ record.vrf.tenant.group }}</a>*
+    {% else %}
+        &mdash;
+    {% endif %}
+    """
+
+    def __init__(self, *args, **kwargs):
+        if 'verbose_name' not in kwargs:
+            kwargs['verbose_name'] = 'Tenant Group'
+
+        super().__init__(template_code=self.template_code, *args, **kwargs)
+
+    def value(self, value):
+        return str(value) if value else None
+