feat(dgw): add recording_storage_is_writeable in heartbeat (#835)

Issue: DGW-175

devolutions-gateway/src/api/heartbeat.rs

@@ -17,6 +17,8 @@ pub(crate) struct Heartbeat {
     version: &'static str,
     /// Number of running sessions
     running_session_count: usize,
+    /// Whether the recording storage is writteable or not.
+    recording_storage_is_writteable: bool,
     /// The total space of the disk used to store recordings, in bytes.
     #[serde(skip_serializing_if = "Option::is_none")]
     recording_storage_total_space: Option<u64>,
@@ -54,6 +56,18 @@ pub(super) async fn get_heartbeat(
         .await
         .map_err(HttpError::internal().err())?;
 
+    let recording_storage_is_writteable = {
+        let probe_file = conf.recording_path.join("probe");
+
+        let is_ok = std::fs::write(&probe_file, ".").is_ok();
+
+        if is_ok {
+            let _ = std::fs::remove_file(probe_file);
+        }
+
+        is_ok
+    };
+
     let (recording_storage_total_space, recording_storage_available_space) = if sysinfo::IS_SUPPORTED_SYSTEM {
         trace!("System is supporting listing storage disks");
 
@@ -98,6 +112,7 @@ pub(super) async fn get_heartbeat(
         hostname: conf.hostname.clone(),
         version: env!("CARGO_PKG_VERSION"),
         running_session_count,
+        recording_storage_is_writteable,
         recording_storage_total_space,
         recording_storage_available_space,
     }))