fix: check response code of CoAP responses

Author: JKRhb

lib/src/binding_coap/coap_client.dart

@@ -193,6 +193,7 @@ class CoapClient extends ProtocolClient {
     }
 
     coapClient.close();
+    response.checkResponseCode();
     return response.content;
   }
 

lib/src/binding_coap/coap_extensions.dart

@@ -153,6 +153,18 @@ extension ResponseExtension on CoapResponse {
     return Content(_contentType, _payloadStream);
   }
 
+  /// Checks the [code] of this [CoapResponse] and throws an [Exception] if it
+  /// should indicate an error.
+  void checkResponseCode() {
+    if (code.isServerError) {
+      throw CoapServerErrorException(this);
+    }
+
+    if (code.isErrorResponse) {
+      throw CoapClientErrorException(this);
+    }
+  }
+
   /// Validates the payload and returns a serialized ACE creation hint if
   /// successful.
   AuthServerRequestCreationHint? get creationHint {