'Checks whether the Proactive Support tab should be shown.
It should only be for TrueNAS and Siver/Gold Customers.
Returns:
tuple(bool, Support instance)'

@classmethod
def is_available(cls, support=None):

    if notifier().is_freenas():
        return (False, support)
    if (support is None):
        try:
            support = cls.objects.order_by('-id')[0]
        except IndexError:
            support = cls.objects.create()
    (license, error) = get_license()
    if (license is None):
        return (False, support)
    if (license.contract_type in (ContractType.silver.value, ContractType.gold.value)):
        return (True, support)
    return (False, support)
