TT#40540 fix Accept Header treatment

the accept header can contain a list of comma-separated values. If only
one of those is application/json or */*, we should send that.

Example of an Accept header:
text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8

Change-Id: I45bdea5dca05060c1cc17ce5bbdff9c58cb5ca72

lib/NGCP/Panel/Role/EntitiesItem.pm

@@ -189,14 +189,14 @@ sub get {
         my $action_config = $self->get_config('action');
 
         if( ( defined $header_accept
-                && ($header_accept ne 'application/json')
-                && ($header_accept ne '*/*')
+                && ($header_accept !~ m!\bapplication/json\b|\b\*/\*\b!) # application/json OR */*
             )
             || ( $action_config->{GET}->{ReturnContentType}
                 && $action_config->{GET}->{ReturnContentType} ne 'application/json'
             )
         ) {
             $self->return_requested_type($c,$id,$item);
+            # in case this method is not defined, we should return a reasonable error explaining the Accept Header
             return;
         }