Disable/Enable external handles using cfg property

[milanmajchrak]

It is shortener.enabled property.

Excel Notes:
TODO: create @disable anotation, DisableFilter.filter method and add this Anotation into the ExternalHandleRestRepository. Create tests

[kosarko]

default by nemel umoznovat vytvoreni handlu z venku (pokud nekdo ani nevi, ze tam to api je, tak by to nemel zjistit tak, ze najde 3000 handlu, ktery u nej nekdo vytvoril). Asi by mohlo byt resitelne defaultnim denylistem, kterej nedovoli nic.