[Zone] Zone Routing Improvements (#4142)

* Routing changes

* Update world_content_service.cpp

* Cleanup routing logic

* Tweaks

zone/doors.cpp

@@ -73,6 +73,15 @@ Doors::Doors(const DoorsRepository::Doors &door) :
 	m_door_param              = door.door_param;
 	m_size                    = door.size;
 	m_invert_state            = door.invert_state;
+
+	// if the target zone is the same as the current zone, use the instance of the current zone
+	// if we don't use the same instance_id that the client was sent, the client will forcefully
+	// issue a zone change request when they should be simply moving to a different point in the same zone
+	// because the client will think the zone point target is different from the current instance
+	if (door.dest_zone == zone->GetShortName() && m_destination_instance_id == 0) {
+		m_destination_instance_id = zone->GetInstanceID();
+	}
+
 	m_destination_instance_id = door.dest_instance;
 	m_is_ldon_door            = door.is_ldon_door;
 	m_dz_switch_id            = door.dz_switch_id;