add internal worker plugin to set fqdn for cli actions

lib/App/Netdisco/Worker/Plugin/Internal/BackendFQDN.pm

@@ -0,0 +1,25 @@
+package App::Netdisco::Worker::Plugin::Internal::BackendFQDN;
+
+use Dancer ':syntax';
+use App::Netdisco::Worker::Plugin;
+use aliased 'App::Netdisco::Worker::Status';
+
+use Net::Domain 'hostfqdn';
+use Scalar::Util 'blessed';
+
+register_worker({ phase => 'check', driver => 'direct' }, sub {
+  my ($job, $workerconf) = @_;
+  my $action = $job->action or return;
+
+  # if the job is running at CLI it may need a BACKEND setting
+  return unless scalar grep {$_ eq $action} @{ setting('deferrable_actions') }
+    and not setting('workers')->{'BACKEND'};
+
+  # this can take a few seconds - only do it once
+  info 'resolving backend hostname...';
+  setting('workers')->{'BACKEND'} ||= (hostfqdn || 'fqdn-undefined');
+
+  debug sprintf 'Backend identity set to %s', setting('workers')->{'BACKEND'};
+});
+
+true;