Custom key/values managed by the Moloco Ads client platform.
It's up to the client ads platform to define the schema for the values and their optionality.
The keys are recommended, but not required, to be prefixed with the reversed
internet domain of the AdCloud client platform company. For example, keys defined
by the client ads platform company "example.com" should have "com.example." as
the prefix.
For complex values, JSON payload is recommended.
Moloco doesn't interpret these data in any way for ads serving.
Upon serving, the custom key/values in the AdAccount, Campaign,
and Creative models will be combined into the serving Creative proto in the order of precedence,
with Creative's value having the highest precedence on the same key.
