Can issue certificate for devices

central_backend/src/devices/device.rs

@@ -5,6 +5,20 @@ pub struct DeviceInfo {
     max_relays: usize,
 }
 
+impl DeviceInfo {
+    pub fn error(&self) -> Option<&str> {
+        if self.reference.trim().is_empty() {
+            return Some("Given device reference is empty or blank!");
+        }
+
+        if self.max_relays == 0 {
+            return Some("Given device cannot handle any relay!");
+        }
+
+        None
+    }
+}
+
 #[derive(Clone, Debug, serde::Serialize, serde::Deserialize, Eq, PartialEq, Hash)]
 pub struct DeviceId(pub String);