docs: add a few explanatory docs

Parsing the code, adding some helpful docs as I go.

libs/sdm-launchpad/src/resources/images/l2_base_node.rs

@@ -136,6 +136,7 @@ impl ManagedContainer for TariBaseNode {
     }
 }
 
+/// A helper struct to track the progress of the initial block download.
 struct Checker {
     progress: SyncProgress,
     identity_sent: bool,
@@ -155,6 +156,10 @@ impl Checker {
 
 #[async_trait]
 impl ContainerChecker<LaunchpadProtocol> for Checker {
+    /// The interval hook in the base node checker is used to query the base node via gRPC for the current sync progress.
+    /// The progress is then reported to the SDM via the `CheckerEvent::Progress` event.
+    /// The task is reported as complete (`READY`) once the `sync_state` value from the `get_sync_progress` RPC call
+    /// is `Done`.
     async fn on_interval(&mut self, ctx: &mut CheckerContext<LaunchpadProtocol>) -> Result<(), Error> {
         if self.ready {
             return Ok(());

libs/sdm/src/image/checker.rs

@@ -68,6 +68,11 @@ impl<P: ManagedProtocol> CheckerContext<P> {
     }
 }
 
+/// Polls a container for the logs and stats, and executes the related hooks for the event. If no events are
+/// received for 1 second, the `on_interval` hook is called. The default implementation of all of the hooks do nothing.
+///
+/// In each of the hooks, a mutable reference to a `CheckerContext` is provided, which can be used to access / update
+/// the log and stats history, and update the progress of a task.
 #[async_trait]
 pub trait ContainerChecker<P: ManagedProtocol>: Send {
     async fn entrypoint(mut self: Box<Self>, mut ctx: CheckerContext<P>) {

libs/sdm/src/image/mod.rs

@@ -32,9 +32,11 @@ pub(crate) use task::ImageTask;
 
 use crate::config::ManagedProtocol;
 
+/// A container that can be managed by SDM.
 pub trait ManagedContainer: fmt::Debug + Send + 'static {
     type Protocol: ManagedProtocol;
 
+
     fn checker(&mut self) -> Box<dyn ContainerChecker<Self::Protocol>> {
         Box::<ReadyIfStarted>::default()
     }