Adds comments for dynamic lane registration.

Author: horned-sphere

server/swimos_agent/src/agent_model/mod.rs

@@ -761,6 +761,9 @@ where
 
         let mut dyn_lane_handlers = vec![];
 
+        // This handles any requests that have been received to open dynamic lanes. Due to complex, interleaved
+        // borrows of non-send variables, it is impractical to extract this out as a function. This macro is a
+        // compromise to avoid duplicating the block of code.
         macro_rules! handle_dyn_lanes {
             () => {
                 for LaneSpawnRequest {
@@ -776,7 +779,7 @@ where
                         let io = context.add_lane(&name, kind, lane_conf).await?;
                         let descriptor = ItemDescriptor::WarpLane {
                             kind,
-                            flags: ItemFlags::TRANSIENT,
+                            flags: ItemFlags::TRANSIENT, // For now, all dynamic lanes are transient.
                         };
                         let result = item_model.register_dynamic_item(&name, descriptor);
                         if let Ok(id) = result {
@@ -795,6 +798,9 @@ where
             };
         }
 
+        // Handle any dynamic lane requests received in the `on_init` event. We don't trigger the
+        // corresponding event handlers yet to respect the contract that `on_start` is the first
+        // event handler to be run in the agent.
         handle_dyn_lanes!();
 
         // Run the agent's `on_start` event handler.
@@ -821,8 +827,11 @@ where
             Ok(_) => {}
         }
 
+        // Handle any dynamic lane requests received in the `on_start` event.
         handle_dyn_lanes!();
 
+        // Run all of the event handlers associated with requests for dynamic lanes. These could have bee
+        // generated by either (or both) of the `on_init` and `on_start` events.
         match run_handler(
             &mut ActionContext::new(
                 &suspended,