improve handling of proxied SSL connections

docs/changelog/7.x.x.txt

@@ -1,4 +1,6 @@
 7.7.18
+ - will now respect X-Forwarded-Proto header
+ - no longer need special Apache configuration to handle SSLPROXY header
  - fixed #10674: CDN URLs are cached across HTTP/HTTPS accesses
  - fixed: Copied assets don't always get URL extensions added
  - fixed #10789: Inbox message states not deleted when a user is deleted

lib/WebGUI/Session/Env.pm

@@ -192,7 +192,12 @@ Returns true if a https request was made.
 
 sub sslRequest {
     my $self = shift;
-    return ($self->get('HTTPS') eq 'on' || $self->get('SSLPROXY') ? 1 : 0);
+    return (
+           $self->get('HTTPS') eq 'on'
+        || $self->get('SSLPROXY')
+        || $self->get('HTTP_SSLPROXY')
+        || $self->get('HTTP_X_FORWARDED_PROTO') eq 'https'
+    );
 }