This MR adds new application setting to network section
`allow_local_requests_from_system_hooks`. Prior to this change
system hooks were allowed to do local network requests by default
and we are adding an ability for admins to control it.
- The most common use case for qualified_domain_validator currently is
to allow blank ([]) but not allow nil. Modify the
qualified_domain_validator to support this use case.
Updating multiple application settings panels through
a single action causes the incorrect action to be shown
when there are errors. Instead, make each panel action
handle both updating and display.
George Koltsov