如何验证映射字段在Ecto模型(而不是在控制器中)中是否具有某个键?

I need to store a map as a field into my database (the data source is JSON). For the data to be valid, the JSON needs to have a certain key, i.e. the key has to be present in the converted Elixir map as well.I need to store a map as a field into my databa