Add condition to return json as string

A condition has been added to check if the returnType is of type 'string'. If so, the json is returned as string directly without converting. This is particularly useful to avoid unnecessary conversion when the returnType is already a string.

src/modules/Elsa.Http/Parsers/JsonHttpContentParser.cs

@@ -30,6 +30,9 @@ public async Task<object> ReadAsync(Stream content, Type? returnType, Cancellati
 
         using var reader = new StreamReader(content, leaveOpen: true);
         var json = await reader.ReadToEndAsync();
+
+        if(returnType == typeof(string))
+            return json;
 
         if (returnType == null || returnType.IsPrimitive)
             return json.ConvertTo(returnType ?? typeof(string))!;