feat: automatically discover inventory (#127)

## Fully automated inventory gathering now works!

Boot up harmony_inventory_agent with `cargo run -p harmony_inventory_agent`
Launch the DiscoverInventoryAgentScore , currently available this way :

`RUST_LOG=info cargo run -p example-cli -- -f Discover -y`

And you will have automatically all hosts saved to the database. Run `cargo sqlx setup` if you have not done it yet.

Co-authored-by: Ian Letourneau <ian@noma.to>
Reviewed-on: #127
Co-authored-by: Jean-Gabriel Gill-Couture <jg@nationtech.io>
Co-committed-by: Jean-Gabriel Gill-Couture <jg@nationtech.io>

harmony_inventory_agent/src/local_presence/discover.rs

@@ -1,10 +1,14 @@
+use log::{debug, error};
 use mdns_sd::{ServiceDaemon, ServiceEvent};
 
 use crate::local_presence::SERVICE_NAME;
 
 pub type DiscoveryEvent = ServiceEvent;
 
-pub fn discover_agents(timeout: Option<u64>, on_event: impl Fn(DiscoveryEvent) + Send + 'static) {
+pub async fn discover_agents<F>(timeout: Option<u64>, on_event: F)
+where
+    F: FnOnce(DiscoveryEvent) -> Result<(), String> + Send + 'static + Copy,
+{
     // Create a new mDNS daemon.
     let mdns = ServiceDaemon::new().expect("Failed to create mDNS daemon");
 
@@ -12,23 +16,24 @@ pub fn discover_agents(timeout: Option<u64>, on_event: impl Fn(DiscoveryEvent) +
     // The receiver will be a stream of events.
     let receiver = mdns.browse(SERVICE_NAME).expect("Failed to browse");
 
-    std::thread::spawn(move || {
+    tokio::task::spawn_blocking(move || {
         while let Ok(event) = receiver.recv() {
-            on_event(event.clone());
+            if let Err(e) = on_event(event.clone()) {
+                error!("Event callback failed : {e}");
+            }
             match event {
                 ServiceEvent::ServiceResolved(resolved) => {
-                    println!("Resolved a new service: {}", resolved.fullname);
+                    debug!("Resolved a new service: {}", resolved.fullname);
                 }
                 other_event => {
-                    println!("Received other event: {:?}", &other_event);
+                    debug!("Received other event: {:?}", &other_event);
                 }
             }
         }
     });
 
     if let Some(timeout) = timeout {
-        // Gracefully shutdown the daemon.
-        std::thread::sleep(std::time::Duration::from_secs(timeout));
+        tokio::time::sleep(std::time::Duration::from_secs(timeout)).await;
         mdns.shutdown().unwrap();
     }
 }