* args are json stringified, so we can see in the log what exactly is going in the mock server * better handling of unset fields. Before this commit, if a field was missing in a record, and no default value was set, it was undefined. With this commit, it is set to false. It is important, when we are working with domains such as ['some_many2one', '=', false] * improve read_group so it can group data by day/month