How to implement default values for Entities

[dmurta1]

Describe what is wrong
There is no explanation on how to set default values for different entities

Describe what was expected
A cookbook section exemplifying how to set default values for $date (most important), $store and at least one more example

Additional context
New users may create 2 different responses/scripts, one with a default value, and another one with a entity to be used as filter, for example

• Response with the keywords "sales", so user can search for sales with a hardcoded date
• Response with the keywords "sales" and "$date", so user can search for sales with a $date as dynamic filter

The example above is a bad pattern, and can be easily replaced by a optional "$date" with a default value