MT#64972 /api/customers email_template auto assign change

* if an email template id is explicitly provided as "null",
  it will be assigned as "null".
* remove email templates auto creation (copy from raw) for
  resellers if they do not have the specific one assigned to them.
  that proved to work contraversal as if a customer doesn't have
  an email template assigned to the reseller, and does not want
  to change their business logic (by explicitly providing "null")
  during POST /api/customers for those templates, the auto creation
  for reseller prevents it and causes complications, as well as
  it's not the intended role for /api/customers to automatically
  affect reseller configuration in such a way.

Change-Id: Ie8cf0bffdd397279260a9601367f4457634ed5c8
(cherry picked from commit e956227ab0)

lib/NGCP/Panel/Controller/API/Customers.pm

@@ -293,6 +293,8 @@ sub POST :Allow {
                         . "' that is assigned to Customer's Contact '$resource->{contact_id}'");
                     return;
                 }
+            } elsif (exists $resource->{$field}) {
+                next;
             } else {
                 next unless $t_def_name;
 
@@ -301,22 +303,7 @@ sub POST :Allow {
                     'me.reseller_id' => $custcontact->reseller_id,
                 })->first;
 
-                unless ($template) {
-                    my $raw_def_template = $c->model('DB')->resultset($t_table)->search({
-                        'me.name' => $t_def_name,
-                        'me.reseller_id' => undef
-                    })->first;
-
-                    unless ($raw_def_template) {
-                        $self->error($c, HTTP_INTERNAL_SERVER_ERROR, "Cannot find basic default template '$t_def_name'");
-                        return;
-                    }
-
-                    my $copy_template = { $raw_def_template->get_inflated_columns };
-                    delete $copy_template->{id};
-                    $copy_template->{reseller_id} = $custcontact->reseller_id;
-                    $template = $c->model('DB')->resultset('email_templates')->create($copy_template);
-                }
+                next unless $template;
 
                 $resource->{$field} = $template->id;
             }