Reword the warning for system_qos

Signed-off-by: Michael X. Grey <[email protected]>

Author: mxgrey

rclrs/src/node/primitive_options.rs

@@ -82,9 +82,12 @@ pub trait IntoPrimitiveOptions<'a>: Sized {
         self.qos(QoSProfile::services_default())
     }
 
-    /// Use the system-defined default quality of service profile. This profile
-    /// is determined by the underlying RMW implementation, so you cannot rely
-    /// on this profile being consistent or appropriate for your needs.
+    /// Use the system-defined default quality of service profile. Topics and
+    /// services created with this default do not use the recommended ROS
+    /// defaults; they will instead use the default as defined by the underlying
+    /// RMW implementation (rmw_fastrtps, rmw_connextdds, etc). These defaults
+    /// may not always be appropriate for every use-case, and may be different
+    /// depending on which RMW implementation you are using, so use caution!
     fn system_qos(self) -> PrimitiveOptions<'a> {
         self.qos(QoSProfile::system_default())
     }