Improve null-safety, error logging, and minor optimizations

- Add null-forgiving operator for schemaNode in JsonSchemaValidator
- Enhance error logging with exception details in JsonSchemaParser
- Optimize property checks and retrieval in JsonSchemaParser
- Remove unused dataQuery serialization in SubmodelController

Author: mm-hsh

source/AAS.TwinEngine.DataEngine/Infrastructure/Providers/PluginDataProvider/Helper/JsonSchemaValidator.cs

@@ -45,7 +45,7 @@ public void ValidateRequestSchema(JsonSchema schema)
 
         try
         {
-            var jsonElement = JsonDocument.Parse(schemaNode.ToJsonString()).RootElement;
+            var jsonElement = JsonDocument.Parse(schemaNode!.ToJsonString()).RootElement;
 
             var result = MetaSchemas.Draft202012.Evaluate(jsonElement, _evaluationOptions);
 

source/AAS.TwinEngine.Plugin.TestPlugin/Api/Submodel/Services/JsonSchemaParser.cs

@@ -35,9 +35,9 @@ private void ValidateRequest(JsonSchema jsonSchema)
                 throw new BadRequestException(ExceptionMessages.RequestBodyInvalid);
             }
         }
-        catch (JsonException)
+        catch (JsonException ex)
         {
-            logger.LogError("Requested schema is not valid");
+            logger.LogError(ex, "Requested schema is not valid");
             throw new BadRequestException(ExceptionMessages.FailedParsingJsonSchema);
         }
     }
@@ -48,12 +48,12 @@ private SemanticTreeNode CreateSemanticTree(JsonSchema jsonSchema)
 
         if (!json.TryGetPropertyValue("properties", out var propsNode) ||
             propsNode is not JsonObject props ||
-            !props.Any())
+            props.Count == 0)
         {
             throw new BadRequestException(ExceptionMessages.InvalidJsonSchemaRootElement);
         }
 
-        var rootProperty = props.First();
+        var rootProperty = ((IList<KeyValuePair<string, JsonNode?>>)props)[0];
         return ProcessProperty(rootProperty.Key, rootProperty.Value!, json);
     }
 

source/AAS.TwinEngine.Plugin.TestPlugin/Api/Submodel/SubmodelController.cs

@@ -26,10 +26,6 @@ public class SubmodelController(ISubmodelHandler submodelHandler) : ControllerBa
     [ProducesResponseType(typeof(ActionResult), StatusCodes.Status500InternalServerError)]
     public async Task<ActionResult<JsonObject>> RetrieveDataAsync([FromBody] JsonSchema? dataQuery, [FromRoute] string submodelId, CancellationToken cancellationToken)
     {
-        var schemaJsonString = JsonSerializer.Serialize(dataQuery, new JsonSerializerOptions
-        {
-            WriteIndented = true // Optional: for human-readable output
-        });
         var decodedSubmodelId = submodelId.DecodeBase64();
         if (dataQuery is null)
         {