fix: tracker checker return error code when it fails

This command:

```
cargo run --bin tracker_checker "./share/default/config/tracker_checker.json" && echo "OK"
```

should not print OK when it fails.

src/bin/tracker_checker.rs

@@ -7,5 +7,5 @@ use torrust_tracker::checker::app;
 
 #[tokio::main]
 async fn main() {
-    app::run().await;
+    app::run().await.expect("Some checks fail");
 }

src/checker/app.rs

@@ -2,18 +2,22 @@ use std::sync::Arc;
 
 use super::config::Configuration;
 use super::console::Console;
+use super::service::{CheckError, Service};
 use crate::checker::config::parse_from_json;
-use crate::checker::service::Service;
 
 pub const NUMBER_OF_ARGUMENTS: usize = 2;
 
+/// # Errors
+///
+/// If some checks fails it will return a vector with all failing checks.
+///
 /// # Panics
 ///
 /// Will panic if:
 ///
 /// - It can't read the json configuration file.
 /// - The configuration file is invalid.
-pub async fn run() {
+pub async fn run() -> Result<(), Vec<CheckError>> {
     let args = parse_arguments();
     let config = setup_config(&args);
     let console_printer = Console {};
@@ -22,7 +26,7 @@ pub async fn run() {
         console: console_printer,
     };
 
-    service.run_checks().await;
+    service.run_checks().await
 }
 
 pub struct Arguments {

src/checker/service.rs

@@ -14,12 +14,24 @@ pub struct Service {
     pub(crate) console: Console,
 }
 
+#[derive(Debug)]
+pub enum CheckError {
+    UdpError,
+    HttpError,
+    HealthCheckError { url: Url },
+}
+
 impl Service {
-    pub async fn run_checks(&self) {
+    /// # Errors
+    ///
+    /// Will return OK is all checks pass or an array with the check errors.
+    pub async fn run_checks(&self) -> Result<(), Vec<CheckError>> {
         self.console.println("Running checks for trackers ...");
+
         self.check_udp_trackers();
         self.check_http_trackers();
-        self.run_health_checks().await;
+
+        self.run_health_checks().await
     }
 
     fn check_udp_trackers(&self) {
@@ -38,11 +50,22 @@ impl Service {
         }
     }
 
-    async fn run_health_checks(&self) {
+    async fn run_health_checks(&self) -> Result<(), Vec<CheckError>> {
         self.console.println("Health checks ...");
 
+        let mut check_errors = vec![];
+
         for health_check_url in &self.config.health_checks {
-            self.run_health_check(health_check_url.clone()).await;
+            match self.run_health_check(health_check_url.clone()).await {
+                Ok(()) => {}
+                Err(err) => check_errors.push(err),
+            }
+        }
+
+        if check_errors.is_empty() {
+            Ok(())
+        } else {
+            Err(check_errors)
         }
     }
 
@@ -62,22 +85,25 @@ impl Service {
             .println(&format!("{} - HTTP tracker at {} is OK (TODO)", "✓".green(), url));
     }
 
-    async fn run_health_check(&self, url: Url) {
+    async fn run_health_check(&self, url: Url) -> Result<(), CheckError> {
         let client = Client::builder().timeout(Duration::from_secs(5)).build().unwrap();
 
         match client.get(url.clone()).send().await {
             Ok(response) => {
                 if response.status().is_success() {
                     self.console
                         .println(&format!("{} - Health API at {} is OK", "✓".green(), url));
+                    Ok(())
                 } else {
                     self.console
                         .eprintln(&format!("{} - Health API at {} failing: {:?}", "✗".red(), url, response));
+                    Err(CheckError::HealthCheckError { url })
                 }
             }
             Err(err) => {
                 self.console
                     .eprintln(&format!("{} - Health API at {} failing: {:?}", "✗".red(), url, err));
+                Err(CheckError::HealthCheckError { url })
             }
         }
     }

src/e2e/runner.rs

@@ -68,7 +68,7 @@ pub fn run() {
     let tracker_checker_config_path =
         create_tracker_checker_config_file(&running_services, temp_dir.temp_dir.path(), TRACKER_CHECKER_CONFIG_FILE);
 
-    // todo: inject the configuration with an env variable so that we don't have 
+    // todo: inject the configuration with an env variable so that we don't have
     // to create the temporary directory/file.
     run_tracker_checker(&tracker_checker_config_path).expect("All tracker services should be running correctly");